# Endangered and Threatened Wildlife and Plants; 12-Month Finding for Purple Lilliput; Threatened Species Status With Section 4(d) Rule for Longsolid and Round Hickorynut and Designation of Critical Habitat

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URL: https://www.frixlaw.com/law-library/documents/fr%3A2020-17015

## Record

- **Collection:** Federal Register
- **Document type:** Proposed Rule
- **Published:** September 29, 2020
- **Citation:** 85 FR 61384

## Text

DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[Docket No. FWS-R4-ES-2020-0010; FF09E21000 FXES11110900000 201]
RIN 1018-BD32
Endangered and Threatened Wildlife and Plants; 12-Month Finding for Purple Lilliput; Threatened Species Status With Section 4(d) Rule for Longsolid and Round Hickorynut and Designation of Critical Habitat

AGENCY:

Fish and Wildlife Service, Interior.

ACTION:

Proposed rule; announcement of 12-month findings.

SUMMARY:

We, the U.S. Fish and Wildlife Service (Service), announce 12-month findings on a petition to list the purple lilliput (
Toxolasma lividum
), longsolid (
Fusconaia subrotunda
), and round hickorynut (
Obovaria subrotunda
) freshwater mussels as endangered or threatened species and to designate critical habitat under the Endangered Species Act of 1973, as amended (Act). We find that listing the longsolid and round hickorynut is warranted. Accordingly, we propose to list the longsolid and round hickorynut as 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 these species to the List of Endangered and Threatened Wildlife and extend the Act's protections to the species. We also propose to designate critical habitat for the longsolid and round hickorynut under the Act. For the longsolid, approximately 1,115 river miles (1,794 kilometers), all of which is occupied by the species, in Pennsylvania, Kentucky, West Virginia, Virginia, Tennessee, and Alabama fall within the boundaries of the proposed critical habitat designation. For the round hickorynut, approximately 921 river miles (1,482 kilometers), all of which is occupied by the species, in Pennsylvania, Ohio, Indiana, Kentucky, West Virginia, Tennessee, Alabama, and Mississippi fall within the boundaries of the proposed critical habitat designation. Finally, we announce the availability of a draft economic analysis of the proposed designation of critical habitat for the longsolid and round hickorynut. After a thorough review of the best available scientific and commercial information, we find that it is not warranted at this time to list the purple lilliput. We ask the public to submit to us at any time new information relevant to the status of purple lilliput or its habitat.

DATES:

For the proposed rule to list and designate critical habitat for the longsolid and round hickorynut, we will accept comments received or postmarked on or before December 28, 2020. 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 November 13, 2020.
Petition finding for the purple lilliput:
For the purple lilliput, the finding in this document was made on September 29, 2020.

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 FWS-R4-ES-2020-0010, which is the docket number for this rulemaking. Then, click on the Search button. On the resulting page, in the Search panel on the left side of the screen, under the Document Type heading, check the Proposed Rule box to locate this document. You may submit a comment by clicking on “Comment Now!”

(2)
By hard copy:
Submit by U.S. mail to: Public Comments Processing, Attn: FWS-R4-ES-2020-0010, 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).

Availability of supporting materials:
For the critical habitat designation, the coordinates or plot points or both from which the maps are generated are included in the administrative record and are available at
https://www.fws.gov/Asheville/
and at
http://www.regulations.gov
under Docket No. FWS-R4-ES-2020-0010. Any additional tools or supporting information that we may develop for the critical habitat designation will also be available at the Service website set out above, and may also be included in the preamble and/or at
http://www.regulations.gov.

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 Act, 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 one year. 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 and designation of critical habitat can only be completed by issuing a rule.

What this document does.
We find that listing the purple lilliput as an endangered or threatened species is not warranted. We propose to list the longsolid and round hickorynut as threatened species with a rule under section 4(d) of the Act, and we propose the designation of critical habitat for these two species.

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 longsolid and round hickorynut 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, mining, and timber operations; direct mortality from dredging; residual impacts (reduced population size) from historical harvest; and the proliferation of invasive, nonnative species. These threats also contribute to 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.

Peer review.
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 10 appropriate specialists regarding the purple lilliput species status assessment (SSA) report, 11 regarding the longsolid SSA report, and 10 regarding the round hickorynut SSA report. We received responses from three, none, and one specialists, respectively; feedback we received informed our findings and this proposed rule. The purpose of peer review is to ensure that our listing determinations, critical habitat designations, and 4(d) rules are based on scientifically sound data, assumptions, and analyses. The peer reviewers have expertise in the biology, habitat, and threats to the species.

Because we will consider all comments and information we receive during the comment period, our final determinations for the longsolid and round hickorynut may differ from this proposal. Based on the new information we receive (and any comments on that new information), we may conclude that either the longsolid or round hickorynut are endangered instead of threatened, or we may conclude that either species does not warrant listing as either an endangered species or a threatened species. Such final decisions would be a logical outgrowth of this proposal, as long as we: (1) Base the decisions on the best scientific and commercial data available after considering all of the relevant factors; (2) do not rely on factors Congress has not intended us to consider; and (3) articulate a rational connection between the facts found and the conclusions made, including why we changed our conclusion.

Acronyms and Abbreviations Used

We use several acronyms and abbreviations throughout the preamble of this finding and proposed rule. To assist the reader, we list them here:

Act = Endangered Species Act of 1973, as amended (16 U.S.C. 1531
et seq.
)

AMD = acid mine and saline drainage

BMP = best management practice

CBD = Center for Biological Diversity

DEA = draft economic analysis

IEM = incremental effects memorandum

HUC = hydrologic unit code

LS = longsolid

ppm = parts per million

RFA = Regulatory Flexibility Act

RH = round hickorynut

SSA = species status assessment

TDEC = Tennessee Department of Environment and Conservation

TVA = Tennessee Valley Authority

Information Requested

For the purple lilliput, we ask the public to submit to us at any time new information relevant to the species' status or its habitat.

For the longsolid and round hickorynut, we intend that any final action resulting from this proposed rule will be based on the best scientific and commercial data available and be as accurate and as effective as possible. Therefore, we request comments or information from other concerned governmental agencies, 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, their habitats, 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 the 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 longsolid and round hickorynut, and that the Service can consider in developing a 4(d) rule for the species. In particular, we seek information concerning the extent to which we should include any of the section 9 prohibitions in the 4(d) rule or whether any other forms of take should be excepted from the prohibitions in the 4(d) rule.

(6) The reasons why we should or should not designate habitat as “critical habitat” under section 4 of the Act, including information to inform the following factors that the regulations identify as reasons why designation of critical habitat may be not prudent:

(a) 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;

(b) 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;

(c) 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; or

(d) No areas meet the definition of critical habitat.

(7) Specific information on:

(a) The amount and distribution of longsolid or round hickorynut habitat;

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

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

(d) What areas not occupied at the time of listing are essential for the conservation of the species. We particularly seek comments:

(i) Regarding whether occupied areas are inadequate for the conservation of the species; and

(ii) Providing specific information regarding whether or not unoccupied areas would, with reasonable certainty, contribute to the conservation of the species and contain at least one physical or biological feature essential to the conservation of the species.

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

(9) Any probable economic, national security, or other relevant impacts of designating any area that may be included in the final designation, and the related benefits of including or excluding specific areas.

(10) Information on the extent to which the description of probable economic impacts in the draft economic analysis is a reasonable estimate of the likely economic impacts (
i.e.,
incremental impacts estimated to be less than $327,000 per year for the next 10 years).

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

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

Please 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.

Public Hearing

Section 4(b)(5) of the Act provides for a public hearing on this proposal for the longsolid and round hickorynut, if requested. We must receive requests for a public hearing, in writing, at 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

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 (referred to below as the CBD petition) to list 404 aquatic, riparian, and wetland species, including the purple lilliput, longsolid, and round hickorynut, as endangered or threatened species under the Act. On September 27, 2011, we published a 90-day finding that the petition contained substantial information indicating listing may be warranted for these three species (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 12-month findings for purple lilliput, longsolid, and round hickorynut to the Office of the Federal Register by June 30, 2020. Subsequently, we requested a 30-day extension that was approved by CBD and granted by the Court on May 12, 2020, whereby the Service would deliver 12-month findings to the Office of the Federal Register by July 30, 2020. This document constitutes our 12-month finding on the April 20, 2010, petition to list the purple lilliput, longsolid, and round hickorynut under the Act, and complies with the October 11, 2019, stipulated settlement agreement and May 12, 2020, extension.

Supporting Documents

An SSA team prepared SSA reports for the purple lilliput, longsolid, and round hickorynut. The SSA team was composed of Service biologists, in consultation with other species experts. The SSA reports represent a compilation of the best scientific and commercial data available concerning the status of these species, including the impacts of past, present, and future factors (both negative and beneficial) affecting these species. As discussed above under
Peer review,
we solicited appropriate peer review of all three of the species' SSA reports. In addition, we sent the draft SSA reports for review to Federal partners, State partners, and scientists with expertise in aquatic ecology and freshwater mussel biology, taxonomy, and conservation. Although we notified tribal nations early in the SSA process for these species, we did not receive any information or comments regarding these species on tribal lands in the United States. The round hickorynut SSA report was also shared with the Canadian government and the Walpole Islands First National Indian Reservation in Canada.

I. Finding for Purple Lilliput

Under section 4(b)(3)(B) of the Act, we are required to make a finding whether or not a petitioned action is warranted within 12 months after receiving any petition that we have determined contains substantial scientific or commercial information indicating that the petitioned action may be warranted (“12-month finding”). We must make a finding that the petitioned action is: (1) Not warranted; (2) warranted; or (3) warranted but precluded. “Warranted but precluded” means that (a) the petitioned action is warranted, but the immediate proposal of a regulation implementing the petitioned action is precluded by other pending proposals to determine whether species are endangered or threatened species, and (b) expeditious progress is being made to add qualified species to the Lists of Endangered and Threatened Wildlife and Plants (Lists) and to remove from the Lists species for which the protections of the Act are no longer necessary. Section 4(b)(3)(C) of the Act requires that, when we find that a

petitioned action is warranted but precluded, we treat the petition as though resubmitted on the date of such finding, that is, requiring that a subsequent finding be made within 12 months of that date. We must publish these 12-month findings in the
Federal Register
.

Summary of Information Pertaining to the Five Factors

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 Services 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' biological response include species-specific factors such as lifespan, reproductive rates or productivity, certain behaviors, and other demographic factors.

In conducting our evaluation of the five factors provided in section 4(a)(1) of the Act to determine whether the purple lilliput (
Toxolasma lividum;
Service 2020a, entire) currently meets the definition of “endangered species” or “threatened species,” we considered and thoroughly evaluated the best scientific and commercial data available regarding the past, present, and future stressors and threats. We reviewed the petition, information available in our files, and other available published and unpublished information. This evaluation may include information from recognized experts; Federal, State, and tribal governments; academic institutions; private entities; and other members of the public. After comprehensive assessment of the best scientific and commercial data available, we determined that the purple lilliput does not meet the definition of an endangered or a threatened species.

The species assessment for the purple lilliput contains more detailed biological information, a thorough analysis of the listing factors, and an explanation of why we determined that this species does not meet the definition of an endangered species or a threatened species. This supporting information can be found on the internet at
http://www.regulations.gov
under docket number FWS-R4-ES-2020-0010. The following is an informational summary for the purple lilliput finding in this document.

Summary of Finding

The purple lilliput is a freshwater mussel that belongs to the order Unionida, also known as the naiads and pearly mussels. Purple lilliput adult mussels are small, with a relatively thick, inflated, oval shell (up to 1.5 inches (in) (38 millimeters (mm)) (Williams et al. 2008, p. 719), and the shell typically darkens with age. The species is currently found in the Great Lakes, Ohio, Cumberland, Tennessee, Arkansas-White-Red, and Lower Mississippi major river basins, within the States of Alabama, Kentucky, Missouri, Arkansas, Ohio, Illinois, Indiana, Michigan, and Tennessee. It is considered extirpated from North Carolina and Georgia, and potentially extirpated from Oklahoma and Virginia. Although it has never been collected within the State of Kansas, it occurs in the Spring River drainage nearby in Missouri, and thus potentially occurs in Kansas, and may eventually be discovered there (Obermeyer et al. 1997, p. 49; Angelo
et al.
2009, p. 95).

Little information is known specific to purple lilliput; thus, we relied on surrogate life-history information for closely related species when necessary, including for sex-specific information, for information on reproduction, and for determining appropriate temperatures for glochidia metamorphosis. For example, the purple lilliput is a short-lived species, estimated to live 5 to 10

years (possibly up to 15 years), based on the life expectancy of the Savannah lilliput (
Toxolasma pullus
) (9 years; Hanlon and Levine 2004, p. 294), lilliput (
T. parvum
) (at least 5 years; Haag and Rypel 2011, p. 229), and Texas lilliput (
T. texasiense
) (11 years; Haag and Rypel 2011, p. 229).

The purple lilliput can be found in a wide range of habitats and a variety of substrates in rivers and streams at depths less than 3.3 feet (ft) (1 meter (m)) (Gordon and Layzer 1989, p. 34). It may be located in coarse substrates such as cobble and gravel, or fine-particle substrates such as packed sand, silty clay, and mud. It is commonly collected in and near shorelines, in backwaters, and in vegetation and root masses in waters just a few centimeters deep. Purple lilliput also exhibits some ability to inhabit lentic (still water) environments (Roe 2002, p. 5). In unimpounded reaches, the species commonly occurs in a range of slow to swift currents, and from shallow, rocky gravel points, mud, and sandbars in overbank areas and embayments (Parmalee and Bogan 1998, p. 231; Williams et al. 2008, p. 720).

The purple lilliput is a suspension-feeder that filters water and nutrients to eat. Its 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). For their first several months, juvenile mussels ingest food through their foot and are thus deposit feeders, although they may also filter interstitial pore water and soft sediments (Yeager et al. 1994, p. 221; Haag 2012, p. 26). Due to the mechanisms by which food and nutrients are taken in, freshwater mussels collect and absorb toxins (Service 2020a, pp. 54-57).

The purple lilliput has a complex life cycle that relies on fish hosts for successful reproduction, similar to other mussels (Service 2020a, pp. 23-25, 29). This complex life history involves an obligate parasitic larval life stage, called glochidia, which are wholly dependent on host fish, including the longear sunfish (
Lepomis megalotis
) and green sunfish (
L. cyanellus
) (Hill 1986, p. 5).

Additional resource needs of the purple lilliput include appropriate water quality and temperatures, and connectivity of aquatic habitat that facilitates dispersal and an abundance of multiple age classes to ensure recruitment.

Status Throughout All of Its Range

We have carefully assessed the best scientific and commercial data available regarding the past, present, and future threats to the purple lilliput, and we evaluated all relevant factors under the five listing factors, including any regulatory mechanisms and conservation measures addressing these stressors. The primary stressors (which are pervasive across the species' range) affecting the purple lilliput's biological status include habitat degradation or loss (
i.e.,
declines in water quality; reduced water levels; riparian and instream fragmentation; and genetic isolation from development, urbanization, contaminants, agricultural activities, impoundments, changing climate conditions, resource extraction, and forest conversion), and impacts associated with invasive and nonnative species.

While threats have acted on the species to reduce available habitat, the purple lilliput persists in 145 of 272 (53 percent) of its historically occupied populations, and its distribution continues to be represented within the six major river basins that it is historically known to occupy. Our projections of purple lilliput viability into the foreseeable future (
i.e.,
approximately 20 to 30 years, which takes into account available climate modeling projections that inform future conditions) suggest that between 10 and 30 populations have a high risk of extirpation, or could become functionally extirpated. However, the purple lilliput is expected to maintain resilient populations (
i.e.,
able to withstand stochastic events arising from random factors) across the six major river basins in which it historically and currently occurs. In other words, we estimate between 116 and 136 populations would continue to be resilient (or between 79 and 93 percent of the currently known populations) into the future. Additionally, we note that the species' host fish has a broad range, and the purple lilliput has the capability to adapt to lentic habitats in certain situations, which is a life-history trait that suggests it may be less susceptible to some potential habitat changes. Thus, after assessing the best available information, we determine that the purple lilliput is not in danger of extinction now or likely to become so in 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. Having determined that the purple lilliput is not in danger of extinction or likely to become so in the foreseeable future throughout all of its range, we now consider whether it may be in danger of extinction or likely to become so in the foreseeable future in a significant portion of its range—that is, whether there is any portion of the species' range for which it is true that both (1) the portion is significant; and, (2) the species is in danger of extinction now or likely to become so in the foreseeable future 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.

In undertaking this analysis for the purple lilliput, 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 or threatened.

We found two areas (Great Lakes and Cumberland River basins) where there may be a concentration of threats acting on the species such that the species in these portions of the range may be endangered or threatened, but we did not find that these areas constituted significant portions of the species' range. Accordingly, we found that the purple lilliput is not in danger of extinction now and is not likely to become so within the foreseeable future in any significant portion 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 purple lilliput does not meet the definition of an endangered species or a threatened species in accordance with sections 3(6) and 3(20) of the Act. Therefore, we find that listing the purple lilliput is not warranted at this time. A detailed discussion of the basis for this finding can be found in the purple lilliput species assessment form, and other

supporting documents, such as the accompanying SSA report (Service 2020a, entire) (see
http://www.regulations.gov
under docket number FWS-R4-ES-2020-0010).

II. Proposed Listing Determination for Longsolid and Round Hickorynut

Background

The longsolid (
Fusconaia subrotunda
) is a freshwater river mussel belonging to the Unionidae family, also known as the naiads and pearly mussels. Longsolid adults are light brown in color, darkening with age. The shell is thick and medium-sized (up to 5 inches (in) (125 millimeters (mm)), and typically has a dull sheen (Williams et al. 2008, p. 322). There is variability in the inflation of the shell depending on population and latitudinal location (Ortmann 1920, p. 272; Watters et al. 2009, p. 130).

The longsolid is currently found in the Ohio, Cumberland, and Tennessee River basins, overlapping within the States of Alabama, Kentucky, New York, North Carolina, Ohio, Pennsylvania, Tennessee, Virginia, and West Virginia (Service 2018, Appendix A; Figure 1, below). It is considered extirpated from Georgia, Indiana, and Illinois. Additionally, it is classified as an endangered species by the State of Ohio, and considered to have various levels of concern, imperilment, or vulnerability (see Table 1-1 in the SSA report) by the States of Alabama, Kentucky, North Carolina, Pennsylvania, Tennessee, Virginia, and West Virginia.

BILLING CODE 4333-15-P

EP29SE20.033

BILLING CODE 4333-15-C

Similar to the longsolid, the round hickorynut also belongs to the Unionidae family of naiads and pearly mussels. Round hickorynut adult mussels are greenish-olive to dark or chestnut brown, sometimes blackish in

older individuals, and may have a yellowish band dorsally (Parmalee and Bogan 1998, p. 168). Inflation of the shell is variable depending on population and latitudinal location (Ortmann 1920, p. 272; Williams et al. 2008, p. 474). The shell is thick, solid, and up to 3 in (75 mm) in length, but usually is less than 2.4 in. (60 mm) (Williams et al. 2008, p. 473; Watters et al. 2009, p. 209). A distinctive characteristic is that the shell is round in shape, nearly circular, and the umbo (the raised portion of the dorsal margin of a shell) is centrally located.

Within the United States, the round hickorynut is currently found in the Great Lakes, Ohio, Cumberland, Tennessee, and Lower Mississippi River basins, overlapping within the States of Alabama, Indiana, Kentucky, Michigan, Mississippi, Ohio, Pennsylvania, Tennessee, and West Virginia (Service 2019, Appendix A; Figure 2, below). It is considered extirpated from Georgia, Illinois, and New York. Additionally, it has State-level conservation status, ranging across various levels of concern, imperilment, or vulnerability (see Table 1-1 in the SSA report), in the States of Alabama, Indiana, Kentucky, Michigan, Pennsylvania, Tennessee, Virginia, and West Virginia. The round hickorynut also occurs within the Canadian Province of Ontario, where it was listed as an endangered species in 2005, due to the loss of and significant declines in populations (Committee on the Status of Species at Risk in Ontario 2013, p. 4); a single remaining population (showing no recruitment (Morris 2018, pers. comm.)) occurs in Lake St. Clair and the East Sydenham River.

BILLING CODE 4333-15-P

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Thorough reviews of the taxonomy, life history, ecology and State listing status of the longsolid and round hickorynut are presented in detail in the SSA reports (Service 2018, pp. 14, 15, 22-30; Service 2019, pp. 14, 15, 22-29).

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 Services 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' biological response include species-specific factors such as lifespan, reproductive rates or productivity, certain behaviors, and other demographic factors.

Analytical Framework

The SSA reports document the results of our comprehensive biological review of the best scientific and commercial data regarding the status of both species, including an assessment of potential threats to the species. The SSA reports do not represent a decision by the Service on whether either species should be proposed for listing as an endangered or threatened species under the Act. They do, however, 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 reports for the longsolid and round hickorynut; the full SSA reports can be found in docket number FWS-R4-ES-2020-0010 on
http://www.regulations.gov,
and on our internet site
https://www.fws.gov/Asheville/.

To assess the longsolid's and round hickorynut's 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 longsolid and round hickorynut, their resources, and the threats that influence both species' current and future condition, in order to

assess each 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 longsolid and round hickorynut. Full descriptions of all needs are available in chapter 4 of the SSA reports (Service 2018, pp. 25-30; Service 2019, pp. 30-36), which can be found in docket number FWS-R4-ES-2020-0010 on
http://www.regulations.gov,
and on our internet site
https://www.fws.gov/Asheville/.
Based upon the best available scientific and commercial information, and acknowledging existing ecological uncertainties (see section 4.3 in the SSA reports), the resource and demographic needs for both the longsolid and round hickorynut are characterized as:

• Clean, flowing water with appropriate water quality and temperate conditions, such as (but not limited to) dissolved oxygen above 2 to 3 parts per million (ppm), ammonia generally below 0.5 ppm total ammonia-nitrogen, temperatures generally below 86 degrees Fahrenheit (°F) (30 degrees Celsius (°C)), and (ideally) an absence of excessive total suspended solids and other pollutants.

• Natural flow regimes that vary with respect to timing, magnitude, duration, and frequency of river discharge events.

• Predominantly silt-free, stable sand, gravel, and cobble substrates.

• Suspended food and nutrients in the water column including (but not limited to) phytoplankton, zooplankton, protozoans, detritus, and dissolved organic matter.

• Availability of sufficient host fish numbers to provide for glochidia infestation and dispersal. Host fish species for the longsolid include (but may not be limited to): Minnows of the family Cyprinidae and stonerollers (genera
Campostoma
sp.), satinfin shiners (
Cyprinella
sp.), eastern shiners (
Notropis
sp.), and highscale shiners (
Luxilus
sp.), as well as potentially freshwater sculpins of the genus
Cottus.
Host fish species documented for the round hickorynut include the banded sculpin (
Cottus carolinae
), eastern sand darter (
Ammocrypta pellucida
), emerald darter (
Etheostoma baileyi
), greenside darter (
Etheostoma blennioides
), Iowa darter (
Etheostoma exile
), fantail darter (
Etheostoma flabellare
), Cumberland darter (
Etheostoma gore
), spangled darter (
Etheostoma obama
), variegate darter (
Etheostoma variatum
), blackside darter (
Percina maculata
), and frecklebelly darter (
Percina stictogaster
).

• Connectivity among populations. Although the species' capability to disperse is evident through historical occurrence of a wide range of rivers and streams, the fragmentation of populations by small and large impoundments has resulted in isolation and only patches of what once was occupied contiguous river and stream habitat. Genetic exchange occurs between and among mussel beds via sperm drift, host fish movement, and movement of mussels during high flow events. For genetic exchange to occur, connectivity must be maintained. Most freshwater mussels, including the longsolid and round hickorynut, are found in mussel beds that vary in size and are often separated by stream reaches in which mussels are absent or rare (Vaughn 2012, p. 983). The species is often a component of a large healthy mussel assemblage within optimal mussel habitats; therefore, the beds in which they occur are necessary for the species to be resilient over time.

Current Conditions

Current (and future) conditions are described using categories that estimate the overall condition (resiliency) of the longsolid and round hickorynut mussel populations. These categories include:

• High—Resilient populations with evidence of recruitment and multiple age classes represented. They are likely to maintain viability and connectivity among populations, and populations are not linearly distributed (
i.e.,
occur in tributary streams within a management unit). Populations are expected to persist in 20 to 30 years and beyond, and withstand stochastic events. (
Thriving; capable of expanding range.
)

• Medium—Spatially restricted populations with limited levels of recruitment or age class structure. Resiliency is less than under high conditions, but the majority of populations (approximately 75 percent) are expected to persist beyond 20 to 30 years. (
Stable; not necessarily thriving or expanding its range.
)

• Low—Small and highly restricted populations, with no evidence of recent recruitment or age class structure, and limited detectability. These populations have low resiliency, are not likely to withstand stochastic events, and potentially will no longer persist in 20 to 30 years. Populations are linearly distributed within a management unit. (
Surviving and observable, but population likely declining.
)

Given the longsolid's and round hickorynut's ranges include lengthy rivers, such as the Ohio, Allegheny, Cumberland, and Tennessee Rivers, all of which include populations fragmented primarily by dams, we identified separate populations for each hydrologic unit code (HUC) (Seaber et al. 1987, entire; U.S. Geological Survey 2018, entire) at the fourth of 12 levels (
i.e.,
HUC-8 watershed). The HUC-8 watersheds are analogous to medium-sized river basins across the United States. Our analysis describes conditions relevant to longsolid and round hickorynut populations and the overarching HUC-8 watersheds, identified herein as a “management unit.” A management unit could harbor one or more populations. See chapter 2 in the SSA reports for further explanation of the analysis methodology (Service 2018, pp. 15-19; Service 2019, pp. 17-22).

Longsolid

The longsolid's current range extends over nine States, including New York, Pennsylvania, West Virginia, Ohio, Kentucky, Virginia, Tennessee, North Carolina, and Alabama; the species is now considered extirpated in Georgia, Illinois, and Indiana. This range encompasses three major river basins (the Ohio, Cumberland, and Tennessee basins); the species now no longer exists in the Great Lakes basin (loss of six historical populations and four management units). In addition, its representation in the Cumberland River basin is currently within a single population and management unit (loss of nine historical populations and eight management units). Overall, the longsolid is presumed extirpated from 63 percent (102 of 162 populations) of its historically occupied populations, including 6 populations (the entirety) in the Great Lakes basin, 65 populations in the Ohio River basin, 9 populations in the Cumberland River basin, and 26 populations in the Tennessee River basin (see Appendix B in the SSA report (Service 2018, pp. 131-154)). Of the current populations, 3 (5 percent) are estimated to be highly resilient, 9 (15 percent) are estimated to be moderately resilient, and 48 (80 percent) are estimated to have low resiliency.

The longsolid was once a common, occasionally abundant component of the mussel assemblage in rivers and streams where it is now extirpated. Examples include the Beaver River, Pennsylvania (Ortmann 1920, p. 276); Ohio River, Pennsylvania (Tolin 1987, p. 11); Mahoning River, Pennsylvania (Ortmann 1920 p. 276); Wabash River, Indiana/Illinois (Cummings et al. 1992, p. 46); Nolin River, Kentucky (Taylor 1983a, p. 111); and the South Fork Holston River, Virginia/Tennessee (Parmalee and Pohemus 2004, p. 234). Significant declines of the longsolid

have been observed and documented in the Ohio and Cumberland Rivers, and in the Muskingum River system, which harbors the last remaining populations (Muskingum, Tuscarawas, and Walhonding) in Ohio (Neel and Allen 1964, p. 434; Watters and Dunn 1993-94, p. 252; Watters et al. 2009, p. 131; Haag and Cicerello 2016, p. 139).

Round Hickorynut

The current range of the round hickorynut extends over nine States, including Alabama, Indiana, Kentucky, Michigan, Mississippi, Ohio, Pennsylvania, Tennessee, and West Virginia; the species is now considered extirpated in Georgia, Illinois, and New York. This range encompasses five major river basins (Great Lakes, Ohio River, Cumberland River, Tennessee River, and Lower Mississippi River). Round hickorynut representation in the Cumberland River basin is restricted to two linear populations within two management units, while it exists in the Lower Mississippi River basin in a single population. Therefore, while the species currently maintains representation from historical conditions, it is at immediate risk of losing 40 percent (2 of 5 basins) of its representation due to these small, isolated populations under a high degree of threats that have resulted from habitat loss and water quality degradation.

Overall, the round hickorynut has lost an approximate 232 of 297 known populations (78 percent), and 104 of 138 management units (75 percent). This includes 25 populations in the Great Lakes basin, 150 populations in the Ohio River basin, 23 populations in the Cumberland River basin, 29 populations in the Tennessee River basin, and 9 populations in the Lower Mississippi River basin (see Appendix B in the SSA report (Service 2019, pp. 191-212)). Of the current populations, 4 (6 percent) are estimated to be highly resilient, 16 (23 percent) are estimated to be moderately resilient, and 45 (69 percent) are estimated to have low resiliency.

The round hickorynut was once a much more common, occasionally abundant, component of the mussel assemblage in rivers and streams across much of the eastern United States. Population extirpations have been extensive and widespread within every major river basin where the round hickorynut is found. Surveys throughout eastern North America have not targeted the round hickorynut specifically, and as a result, there could have been additional population losses or declines that have gone undocumented. Conversely, it is possible that there are populations that have gone undetected. However, the majority of the species' range has been relatively well-surveyed for freshwater mussel communities, and the likelihood is small that there are substantial or stronghold populations that are undetected. Patterns of population extirpation and declines are pronounced particularly in the Ohio River basin, which appears to be the basin most important for redundancy and representation for the species, due to its documented historical distribution and remaining concentration of populations within the basin.

Populations of the round hickorynut have been apparently lost from entire watersheds and management units in which the species once occupied multiple tributaries, such as the Allegheny, Coal, Little Scioto, Miami, and Vermilion River management units in the Ohio River basin. The State of Ohio, for example, has lost 53 populations of round hickorynut, along with 19 management units (Watters et al. 2009, p. 210). The species is also critically imperiled in Canada, and as a result, the future of the species in Canada may be reliant on hatchery-supported activities or augmentation activities coordinated with the United States.

Precipitous declines and extirpations of round hickorynut populations have been documented in the Great Lakes, Ohio, Cumberland, Tennessee, and Lower Mississippi basins. These declines and extirpations are exhibited in museum collections and reported in published literature accounts of the species (see Appendix D in the SSA report (Service 2019, pp. 214-238)). While this documentation could be a result of more intensive survey effort in the core of the species' distribution, regardless, the extirpation of formerly abundant and extensive populations is a cautionary note for current and future condition projections, and has been most pronounced in the Ohio and Cumberland basins.

Examples of rivers where the round hickorynut is extirpated within these basins include: Crooked Creek, Pennsylvania (Ortmann 1913, p. 298); West Branch Mahoning River, Ohio (Swart 1940, p. 42); Coal River, West Virginia (Carnegie Museum and University of Michigan Museum of Zoology records); Olentangy River, Ohio (Stein 1963, p. 109); Alum Creek, Ohio (Ohio State University, Marion records); Blaine Creek, Kentucky (Bay and Winford 1984, p. 19); Embarras River, Illinois (Parmalee 1967, p. 80); Big Vermilion River, Illinois (Parmalee 1967, p. 80); Cumberland River, Kentucky (Neel and Allen 1964, p. 442); Stones River, Tennessee (Ohio State University, Marion records); and Red River, Tennessee/Kentucky (Ohio State University, Marion records).

Threats Analysis

The following discussions include evaluations of three threats and associated sources that are affecting the longsolid and round hickorynut, and their habitats: (1) Habitat degradation or loss, (2) invasive and nonnative species, and (3) negative effects associated with small population size (Service 2018 and 2019, chapter 6). We note that potential impacts associated with overutilization were evaluated, but we found no evidence of current effects on the species' viability (noting historical effects from harvest on the longsolid that no longer occur). 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 either species based on current knowledge (Service 2018, pp. 70, 73-74; Service 2019, pp. 91-95). Finally, we also considered effects associated with enigmatic population declines, 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 unknown (Haag 2019, p. 43). In some cases, the instream habitat often remains basically intact and continues to support other aquatic organisms such as fish and crayfish. Full descriptions of each of the threats and their sources, including specific examples across the species' range where threats are impacting the species or its habitat, are available in chapter 6 and Appendix A of the SSA reports (Service 2018, pp. 43-76, 134-157; Service 2019, pp. 58-96, 169-187).

Habitat Degradation or Loss

Development/Urbanization

Development and urbanization activities that may contribute to longsolid and round hickorynut habitat degradation and 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 longsolid and round hickorynut include:

(1) 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, high-velocity discharges can cause species living in streams (including mussels) to become stressed, displaced, or killed by fast moving water and the debris and sediment carried in it. Displaced individuals may be left stranded out of the water once floodwaters recede.

(2) Water Quality:
Pollutants (
e.g.,
gasoline, oil drips, fertilizers) that accumulate on impervious surfaces may be washed directly into streams during storm events. Contaminants contained in point and non-point source discharges degrade water and substrate quality, and can result in reduced survival, growth, and reproduction of mussels.

(3) Water Temperature:
During warm weather, rain that falls on impervious surfaces becomes superheated and can stress or kill freshwater species when it enters streams.

Other development-related impacts to the longsolid and round hickorynut, or their habitat, may occur as a result of:

• Water infrastructure. This includes water supply, reclamation, and wastewater treatment, which results in pollution point discharges to streams. Concentrations of contaminants (including nitrogen, phosphorus, chloride, insecticides, polycyclic aromatic hydrocarbons, and personal care products) increase with urban development (Giddings et al. 2009, p. 2; Bringolf et al. 2010, p. 1,311).

• Utility crossings and right-of-way maintenance. Direct impacts from utility crossings include direct exposure or crushing of individuals, sedimentation, and habitat disturbance. The greatest cumulative impact involves cleared rights-of-way that result in direct runoff and increased stream temperature at the crossing location, and potentially promote maintenance utility and all-terrain vehicle access from the rights-of-way (which destroys banks and instream habitat, and thus can lead to increased erosion (see also Service 2017, pp. 48-49)).

• Anthropogenic activities. These types of activities may act to lower water tables, making the longsolid or round hickorynut susceptible to depressed flow levels. Water withdrawals for irrigation, municipal, and industrial water supplies are an increasing concern due to expanding human populations. Water infrastructure development, including water supply, reclamation, and wastewater treatment, results in pollution point discharges to streams. Concentrations of contaminants (including nitrogen, phosphorus, chloride, insecticides, polycyclic aromatic hydrocarbons, and personal care products) increase with urban development (Giddings et al. 2009, p. 2; Bringolf et al. 2010, p. 1,311). It is currently unknown whether anthropogenic effects of development and urbanization are likely to impact the longsolid or round hickorynut at the individual or population level. However, secondary impacts such as the increased likelihood of potential contaminant introduction, stream disturbance caused by impervious surfaces, barrier construction, and forest conversion are likely to act cumulatively on longsolid and round hickorynut populations.

Agricultural activities are pervasive across the range of the longsolid and round hickorynut. Examples include (but are not limited to):

• Longsolid: Agricultural erosion is listed among the factors affecting the Clinch and Powell Rivers (Ahlstedt et al. 2016, p. 8).

• Longsolid: Sedimentation and other non-point source pollution, primarily of agricultural origin, are identified as a primary threat to aquatic fauna of the Nolichucky River (The Tennessee Valley Authority (TVA) 2006, p. 11).

• Longsolid: Agricultural impacts have been noted to take a toll on mussel fauna in the Goose Creek watershed on the South Fork Kentucky River (Evans 2010, p. 15).

• Longsolid and round hickorynut: The Elk River in Tennessee is a watershed with significant agricultural activity (Woodside et al. 2004, p. 10).

• Round hickorynut: Water withdrawals for irrigation for agricultural uses have increased recently in the Tippecanoe River (Fisher 2019, pers. comm.)

• Round hickorynut: Sedimentation and other point and non-point source pollution, primarily of agricultural origin, are identified as a primary threat to aquatic fauna of Big Darby Creek and Killbuck Creek, Ohio (Ohio Department of the Environmental Protection Agency 2004, p. 1; Ohio Department of the Environmental Protection Agency 2011, p. 31).

• Round hickorynut: Approximately 25 percent of the land use area in the West Fork River management unit in West Virginia is in agriculture, and has increased by as much as 9 percent in recent years (U.S. Department of Agriculture 2010, p. 8).

• Round hickorynut: Large-scale mechanized agricultural practices threaten the last remaining population in the Lower Mississippi River basin, in the Big Black River, where the species has already undergone range reduction (Peacock and James 2002, p. 123).

• Round hickorynut: The Duck, Buffalo, and Elk Rivers in Tennessee are watersheds with significant agricultural activity in their headwaters and tributaries, and are a suspected cause for mussel community declines throughout those rivers (Reed 2014, p. 4).

Transportation

Transportation-related impacts include both road development and river navigation. By its nature, 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, changes in sedimentation levels, and increased heavy metals (especially lead), salts, organics, and nutrients to stream systems (Trombulak and Frissell 2000, p. 18). The adding of salts through road de-icing results in high salinity runoff, which is toxic to freshwater mussels. In addition, a major impact of road development is improperly constructed culverts at stream crossings, which can act as barriers if flow through the culvert varies significantly from the rest of the stream, or if the culvert ends up becoming perched (
i.e.,
sitting above the downstream streambed), and fishes that serve as mussel hosts cannot pass through them.

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 bed load, 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 longsolid and round hickorynut, and alter habitats for host fish. Changes in both the water velocity and deposition of sediments not only alters physical habitat, but the associated increases in turbulence, suspended sediment, and turbidity affect mussel feeding and respiration (Aldridge et al. 1987, p. 25). The scope of channel maintenance activities over extensive areas alters physical habitat and degrades water quality. 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 longsolid and round hickorynut include (but are not limited to) the following examples:

• Channelization and dredging—Longsolid populations in the Eel, Vermilion, and Embarras Rivers and Killbuck Creek are extirpated. Round hickorynut populations in the Vermilion and Embarras Rivers are extirpated, while populations in the Eel and Killbuck Creek management units are in low condition; these streams have been extensively dredged and channelized (Butler 2007, p. 63; Appendix B). Additionally, dredging is identified by Taylor (1983b, p. 3) as the primary cause for suitable habitat loss in the Kanawha River (below river mile 79) in West Virginia.

• Barge traffic, which includes construction of fleeting areas, mooring cells, docking facilities, and propeller wash, destroys and disrupts mussel habitat, currently affecting at least 15 (25 percent) of the longsolid populations in the Ohio, Cumberland, and Tennessee River basins (Hubbs et al. 2006, p. 169; Hubbs 2012, p. 3; Smith and Meyer 2010, p. 555; Sickel and Burnett 2005, p. 7; Taylor 1983b, p. 5). All six of the Ohio River mainstem longsolid populations that are considered in low condition are affected by channel maintenance and navigation operations; at least five (8 percent) of the round hickorynut populations in the Ohio basin are affected.

• Channel maintenance and navigation are affecting the low condition populations in the lower Allegheny and Tennessee Rivers due to their clustered distribution and proximity to locks and dams. For the longsolid, these include two Allegheny River populations below Redbank, Pennsylvania (Smith and Meyer 2010, p. 556), and three low condition populations in the Tennessee River main stem above Kentucky Dam.

• Although most prevalent on the mainstem Ohio and Tennessee Rivers, commerce and commercial navigation currently affect round hickorynut populations in the Black and Muskingum Rivers.

Contaminants

Contaminants contained in point and non-point discharges can degrade water and substrate quality and adversely impact mussel populations. Although chemical spills and other point sources of contaminants may directly result in mussel mortality, widespread decreases in density and diversity may result in part from the subtle, pervasive effects of chronic, low-level contamination (Naimo 1995, p. 354). The effects of heavy metals, ammonia, and other contaminants on freshwater mussels were reviewed by Mellinger (1972), Fuller (1974), Havlik and Marking (1987), Naimo (1995), Keller and Lydy (1997), and Newton et al. (2003).

The effects of contaminants such as metals, chlorine, and ammonia are profound on juvenile mussels (Augspurger et al. 2003, p. 2,571; Bartsch et al. 2003, p. 2,566). Juvenile mussels may readily ingest contaminants adsorbed to sediment particles while pedal feeding (Newton and Cope 2007, p. 276). These contaminants also affect mussel glochidia, which are sensitive to some toxicants (Goudreau et al. 1993, p. 221; Jacobson et al. 1997, p. 2,386; Valenti et al. 2005, p. 1,243).

Mussels are noticeably intolerant of heavy metals (Havlik and Marking 1987, p. 4). Even at low levels, certain heavy metals may inhibit glochidial attachment to fish hosts. Cadmium appears to be the heavy metal most toxic to mussels (Havlik and Marking 1987, pp. 4-9), although chromium, copper, mercury, and zinc also negatively affect biological processes (Naimo 1995, p. 355; Jacobson et al. 1997, p. 2,389; Valenti et al. 2005, p. 1,243). Chronic mercury contamination from a chemical plant on the North Fork Holston River, Virginia, destroyed a diverse mussel fauna downstream of Saltville, Virginia, and potentially contributed to the extirpation of the longsolid from that river (Brown et al. 2005, p. 1,459). An example of long-term declines and extirpation of mussels attributed to copper and zinc contamination originating from wastewater discharges at electric power plants includes the Clinch River in Virginia (a portion of which the longsolid currently occupies) (Zipper et al. 2014, p. 9). This highlights that, despite localized improvements, these metals can stay bound in sediments, affecting recruitment and densities of the mussel fauna for decades (Price et al. 2014, p. 12; Zipper et al. 2014, p. 9).

Examples of contaminant-related impacts across the range of longsolid and/or round hickorynut include (but are not limited to):

• Contaminants have affected mussel glochidia on the Clinch River, which is a stronghold population for the longsolid (Goudreau et al. 1993, p. 221; Jacobson et al. 1997, p. 2,386; Valenti et al. 2005, p. 1,243); round hickorynut is now considered extirpated in the Tennessee section of the river.

• The toxic effects of high salinity wastewater from oil and natural gas drilling on juvenile and adult freshwater mussels were observed in the Allegheny River, Pennsylvania, and in the Ohio River basin (Patnode et al. 2015, p. 55).

• Numerous streams throughout both species' ranges have experienced mussel and fish kills from toxic chemical spills, such as Fish Creek in Indiana for the round hickorynut (Sparks et al. 1999, p. 12), and the upper Tennessee River system in Virginia for the longsolid (Ahlstedt et al. 2016, p. 8; Neves 1987, p. 9; Jones et al. 2001, p. 20; Schmerfeld 2006, p. 12). Also in the Tennessee River basin, high counts of coliform bacteria originating from wastewater treatment plants have been documented, contributing to degradation of water quality being a primary threat to aquatic fauna (Neves and Angermeier 1990, p. 50).

• Heavy metals and their toxicity to mussels have been documented in the Great Lakes, Clinton, Muskingum, Ohio, Fox, Powell, Clinch, and Tennessee Rivers where one or both of these species occur (Havlik and Marking 1987, pp. 4-9; van Hees et al. 2010, p. 606). Coal plants are also located on the Kanawha, Green, and Cumberland Rivers, and the effects of these facilities on water quality and the freshwater mussel fauna, including the longsolid and round hickorynut, are likely similar.

The degradation of water quality as a result of land-based oil and gas drilling activities is a significant adverse effect on freshwater mussels, and specifically on longsolid in the Ohio River basin and populations in the Allegheny River, as well as the in Kanawha, Little Kanawha, and Elk Rivers.

Agricultural Activities

The advent of intensive row crop agricultural practices has been cited as a potential factor in freshwater mussel decline and species extirpation in the eastern United States (Peacock et al.

2005, p. 550). Nutrient enrichment and water withdrawals, which are threats commonly associated with agricultural activities, are most likely to affect individual longsolid and round hickorynut mussels, although in some instances may be localized and limited in scope. However, chemical control using pesticides, including herbicides, fungicides, insecticides, and their surfactants and adjuvants, are highly toxic to juvenile and adult freshwater mussels (Bringolf et al. 2007, p. 2,092). Waste from confined animal feeding and commercial livestock operations is another potential source of contaminants that comes from agricultural runoff. The concentrations of these contaminants that emanate from fields or pastures may be at levels that can affect an entire population, especially given the highly fragmented distributions of the longsolid and round hickorynut (also see
Contaminants,
above).

Agencies such as the Natural Resources Conservation Service and 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 of stream banks and shorelines, thus reducing erosion. However, the overall effectiveness of these programs over a large scale is unknown given the longsolid's and round hickorynut's wide distribution and varying agricultural intensities.

Given the large extent of private land and agricultural activities within the ranges of the longsolid and round hickorynut, the effects of agricultural activities that degrade water quality and result in habitat deterioration are not frequently detected until after the event(s) occur. In summary, agricultural activities are pervasive across the ranges of the longsolid and round hickorynut. The effects of agricultural activities on the longsolid and round hickorynut are a factor in their historical decline and localized extirpations.

Agricultural activities are pervasive across the range of the longsolid and round hickorynut. Specifically, agricultural impacts have affected and continue to affect high, medium, and low condition longsolid populations within these basins, including:

• Longsolid only: French Creek and Allegheny River (Pennsylvania), Hughes River (West Virginia), Tuscawaras River (Ohio), Rolling Fork River (Kentucky), Little River and Valley River (North Carolina), Nolichucky River (Tennessee), Clinch and Powell Rivers (Tennessee and Virginia), and Estill Fork (Alabama).

• Round hickorynut only: Pine, Belle, and Black Rivers (Michigan).

• Both species: Shenango River (Pennsylvania); Elk, Little Kanawha, and North Fork Hughes Rivers (West Virginia); Licking and Kentucky Rivers (Kentucky); Elk and Buffalo Rivers (Tennessee); and Paint Rock River (Alabama).

Dams and Barriers

The effects of impoundments and barriers on aquatic habitats and freshwater mussels are relatively well-documented (Watters 2000, p. 261). Dams alter and disrupt connectivity, and alter water quality, which affect longsolid and round hickorynut species. Extinction/extirpation of 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). Humans have constructed dams for a variety of reasons: flood prevention, water storage, electricity generation, irrigation, recreation, and navigation (Eissa and Zaki 2011, p. 253). Dams, either natural (by beavers or by aggregations of woody debris) or manmade, have many impacts on stream ecosystems. Reductions in the diversity and abundance of mussels are primarily attributed to habitat shifts caused by impoundments (Neves et al. 1997, p. 63). The survival of mussels and their overall reproductive success are influenced:

•
Upstream of dams,
by the change from flowing to impounded waters, increased depths, increased buildup of sediments, decreased dissolved oxygen, and the drastic alteration in resident fish populations.

•
Downstream of dams,
by fluctuations in flow regimes, minimal releases and scouring flows, seasonal depletion of dissolved oxygen, reduced or increased water temperatures, and changes in fish assemblages.

Additionally, improperly constructed culverts at stream crossings may act as barriers and have some similar negative effects as dams on stream systems. Fluctuating flows through the culvert can vary significantly from the rest of the stream, preventing fish passage and scouring downstream habitats. For example, if a culvert sits above the streambed, aquatic organisms cannot pass through it. These barriers fragment habitats along a stream course and contribute to genetic isolation of the aquatic species inhabiting the streams.

Whether constructed for purposes such as flood control, navigation, hydropower, water supply or multi-purpose uses, the construction and continued operation of dams (per existing licensing schedules) is a pervasive negative influence on the longsolid, round hickorynut, and their habitats throughout their ranges. Although there are recent efforts to remove older, failing dams within the ranges of the longsolid and round hickorynut, such as Lock and Dam 6 on the Green River, and current plans to remove others, such as Six Mile Dam on the Walhonding River, dams and their effects on longsolid and round hickorynut population distributions have had perhaps the greatest documented negative influence on these species (Hardison and Layzer 2001, p. 79; Layzer et al. 1993, p. 68; Parmalee and Polhemus 2004, p. 239; Smith and Meyer 2010, p. 543; Hubbs 2012, p. 8; Watters and Flaute 2010, p. 2).

Over 20 of the rivers and streams currently occupied by the longsolid are directly affected by dams, thus directly influencing the species' distribution rangewide. For the round hickorynut, all occupied rivers and streams are directly or indirectly affected by dams. See section 6.1.5 of the SSA reports for specific areas where dams and other impoundments occur within the range of the species (Service 2018, pp. 59-63; Service 2019, pp. 73-77).

Changing Climate Conditions

Changing climate conditions that can influence freshwater mussels include increasing or decreasing water temperatures and precipitation patterns that result in increased flooding, prolonged droughts, or reduced stream flows, as well as changes in salinity levels (Nobles and Zhang 2011, pp. 147-148). An increase in the number of days with heavy precipitation over the next 25 to 35 years is expected across the longsolid's range (U.S. Global Climate Change Research Program 2017, p. 207). Although changing climate conditions have potentially affected the longsolid to date, the timing, frequency, and extent of these effects is currently unknown. Possible impacts to the species could include alteration of the fundamental ecological processes, such as thermal suitability; changes in seasonal patterns of precipitation and runoff, which could alter the hydrology of streams; and changes in the presence

or combinations of invasive, native or nonnative species.

We examined information on anticipated climate effects to wide-ranging mussels, which included a study that used RCP 2.6 and 8.5 and was conducted on the federally endangered spectaclecase (
Cumberlandia monodonta
). Our analysis of the best available climate change information revealed that within the range of both the longsolid and round hickorynut, shifts in the species-specific physiological thresholds in response to altered precipitation patterns and resulting thermal regimes are possible. Additionally, the expansion of invasive, nonnative species because of climatic changes has the potential for long-term detriments to the mussels and their habitats. Other potential impacts are associated with changes in food web dynamics and the genetic bottleneck that can occur with low effective population sizes (Nobles and Zhang 2011, p. 148). The influences of these changes on the longsolid and round hickorynut are possible in the future (see Scenario 3,
Future Conditions,
below). Multi-scale climate models that can be interpreted at both the rangewide and population levels, and are tailored to benthic invertebrates, which incorporate genetic and life-history information, are needed before the longsolid and round hickorynut declines can be correlated with climate change. At this time, the best available information indicates that climate change is considered a secondary factor influencing the viability of the longsolid and round hickorynut and is not currently thought to be a primary factor in the longsolid's or round hickorynut's occurrence and distribution across their ranges.

Resource Extraction

The most intensive resource extraction activities affecting the longsolid, round hickorynut, and their habitats are coal mining and oil and gas exploration, which are summarized here. Additional less intensive resource extraction activities affecting the species include gravel mining/dredging, which is detailed in the SSA reports (Service 2018, pp. 64-65; Service 2019, pp. 79-83).

Activities associated with coal mining and oil and gas drilling can contribute chemical pollutants to streams. Acid mine and saline drainage (AMD) is created from the oxidation of iron-sulfide minerals such as pyrite, forming sulfuric acid (Sams and Beer 2000, p. 3). This AMD may be associated with high concentrations of aluminum, manganese, zinc, and other constituents (Tennessee Department of Environment and Conservation (TDEC) 2014, p. 72). These metals, and the high acidity typically associated with AMD, can be acutely and chronically toxic to aquatic life (Jones 1964, p. 96).

Natural gas extraction has negatively affected water quality through accidental spills and discharges, as well as increased sedimentation due to increases in impervious surface and tree removal for drill pads and pipelines (Vidic et al. 2013, p. 6). Disposal of insufficiently treated brine wastewater is known to adversely affect freshwater mussels (Patnode et al. 2015, p. 62). Contaminant spills are also a concern.

Sediment appears to be the largest impact to mussel physical habitat in streams as a result of gas extraction activities (Clayton 2018, pers. comm.). Excessive suspended sediments can impair feeding processes, leading to acute short-term or chronic long-term stress. Both excessive sedimentation and excessive suspended sediments can lead to reduced mussel fitness (Ellis 1936, p. 29; Anderson and Kreeger 2010, p. 2). This sediment is generated by construction of the well pads, access roads, and pipelines (for both gas and water).

Examples of the variety of resource extraction activities (coal, oil, gas, and gravel mining) that occur across the range of the longsolid and round hickorynut include (but are not limited to):

• Longsolid: The Cumberland Plateau and Central Appalachian regions of Tennessee and Kentucky (upper Cumberland River system and upper Tennessee River system) continue to experience mining activity that impairs water quality in streams (TDEC 2014, p. 62).

• Longsolid: High levels of copper, manganese, and zinc, metals toxic to freshwater mussels, were found in sediment samples from both the Clinch and Powell Rivers, and mining impacts close to Big Stone Gap, Virginia, have almost eliminated the mussel fauna in the upper Powell River. The longsolid is considered extirpated from the South Fork Powell River and Cane Creek, both tributaries to the upper portion of the Powell River (Ahlstedt and Tuberville 1997, p. 75; Appendix D).

• Round hickorynut: Although populations persist in the Rockcastle River and Buck Creek in the Cumberland basin, coal and gravel mining continues to occur in these watersheds.

• Round hickorynut: The extensive mining of gravel in riparian zones reduces vegetative buffers and causes channel instability, and has been implicated in mussel declines in the Walhonding River, Ohio, which harbors a low condition population (Hoggarth 1995-96, p. 150).

• Both species: Impacts from natural gas pipelines have a high potential to occur in West Virginia and Pennsylvania. Tank trucks hauling such fluids can overturn into mussel streams, which recently occurred in Meathouse Fork of Middle Island Creek (Clayton 2018, pers. comm.).

• Both species: Natural gas extraction in the Marcellus Shale region (the largest natural gas field in the United States that runs through northern Appalachia) has negatively affected water quality through accidental spills and discharges in populations in the Shenango, Elk, Little Kanawha, and Kanawha management units.

• Both species: Coal mining has been implicated in sediment and water chemistry impacts in the Kanawha River in West Virginia, potentially limiting the Elk River populations of both species (Morris and Taylor 1978, p. 153).

• Both species: Resource extraction and AMD have been cited as contributors to the loss of mussel species in the Cumberland basin (Haag and Cicerello 2016, p. 15), including the loss of longsolid from Rockcastle and Caney Fork Rivers, and the loss of round hickorynut in the Caney Fork, Little South Fork, Big South Fork, and Cumberland Rivers (Anderson et al. 1991, p. 6; Layzer and Anderson 1992, p. 97; Warren and Haag 2005, p. 1,383).

• Both species: In the upper Kentucky River watershed, where both species exhibit a lack of recruitment (and also the Red River for round hickorynut), historical un-reclaimed mines and active coal mines are prevalent (Kentucky Department for Environmental Protection 2015, p. 66).

Forest Conversion

Silvicultural activities, when performed according to strict forest practices guidelines or best management practices (BMPs), can retain adequate conditions for aquatic ecosystems; however, when forest practices guidelines or BMPs are not followed, these activities can also cause measurable impacts and contribute to the myriad of stressors facing aquatic systems throughout the eastern United States (Warrington et al. 2017, p. 8). Both small- and large-scale forestry activities have an impact depending on the physical, chemical, and biological characteristics of adjacent streams (Allan and Castillo 2007, p. 107).

Clearing large areas of forested wetlands and riparian systems

eliminates shade once provided by tree canopies, exposing streams to more sunlight and increasing the in-stream water temperature (Wenger 1999, p. 35). The increase in stream temperature and light after deforestation alters macroinvertebrate (and other aquatic species) richness, abundance, and composition in streams to various degrees depending a species' tolerance to temperature change and increased light in the aquatic system (Kishi et al. 2004, p. 283; Couceiro et al. 2007, p. 272; Caldwell et al. 2014, p. 2,196).

Sediment runoff from cleared forested areas is a known stressor to aquatic systems (
e.g.,
Webster et al. 1992, p. 232; Jones III et al. 1999, p. 1,455; Broadmeadow and Nisbet 2004, p. 286; Aust et al. 2011, p. 123). The physical characteristics of stream channels are affected when large quantities of sediment are added or removed (Watters 2000, p. 263). Mussels and fishes are potentially affected by changes in suspended and bed material load, changes in bed sediment composition associated with increased sediment production and runoff, changes in channel formation, stream crossings, and inadequately buffered clear-cut areas, all of which can be sources of sediment entering streams (Taylor et al. 1999, p. 13).

Forest conversion has occurred across the range of the longsolid and round hickorynut. Siltation and erosion from natural forest conversion to monoculture and intensive forestry practices without BMPs is a well-documented stressor to aquatic systems throughout the eastern United States (Warrington et al. 2017, p. 8). Forest conversion has been documented in all basins in which these species occur.

Invasive and Nonnative Species

When a nonnative species is introduced into an ecosystem, it may have many advantages over native species, such as easy adaptation to varying environments and a high tolerance of living conditions that allow it to thrive in its new habitat. There may not be natural predators to keep the nonnative species in check; therefore, it can potentially live longer and reproduce more often, further reducing the biodiversity in the system. The native species may become an easy food source for invasive, nonnative species, or the invasive species may carry diseases that extirpate populations of native species. Invasive, nonnative species are pervasive across the longsolid's and round hickorynut's ranges. Examples of invasive, nonnative species that affect freshwater mussels like the longsolid and round hickorynut are the Asian clam (
Corbicula fluminea
), zebra mussel (
Dreissena polymorpha
), quagga mussel (
Dreissena bugensis
), black carp (
Mylopharyngodon piceus
), didymo (also known as rock snot;
Didymosphenia geminata
), and hydrilla (also known as water-thyme;
Hydrilla verticillata
).

• The Asian clam alters benthic substrates, may filter mussel sperm or glochidia, competes with native species for limited resources, and causes ammonia spikes in surrounding water when they die off en masse (Scheller 1997, p. 2).

• Dreissenid mollusks, such as the zebra mussel and quagga mussel, adversely affect native species through direct colonization, reduction of available habitat, changes in the biotic environment, or a reduction in food sources (MacIsaac 1996, p. 292). Zebra mussels are also known to alter the nutrient cycle in aquatic habitats, affecting other mollusks and fish species (Strayer 1999, p. 22).

• Given their size and diet preferences, black carp have the potential to restructure benthic communities by direct predation and removal of algae-grazing snails. Mussel beds consisting of smaller individuals and juvenile recruits are probably most vulnerable to being consumed by black carp (Nico et al. 2005, p. 192). Furthermore, because black carp attain a large size (well over 3.28-ft (1-m) long), and their life span is reportedly over 15 years, they are expected to persist for many years. Therefore, they have the potential to cause harm to native mollusks by way of predation on multiple age classes (Nico et al. 2005, p. 77).

• The two nonnative plant species that are most problematic for the longsolid and round hickorynut (
i.e.,
impacting the species throughout their ranges) are hydrilla and didymo. Hydrilla is an aquatic plant that alters stream habitat, decreases flows, and contributes to sediment buildup in streams (National Invasive Species Council Management Plan 2018, p. 2). High sedimentation can cause suffocation, reduce stream flow, and make it difficult for mussels' interactions with host fish necessary for development. Didymo can alter the habitat and change the flow dynamics of a site (Jackson et al. 2016, p. 970). Invasive plants grow uncontrolled and can smother habitat, affect flow dynamics, alter water chemistry, and increase water temperatures, especially in drought conditions (Colle et al. 1987, p. 416).

Effects Associated With Small Population Size

Without the level of population connectedness that the species experienced historically (
i.e.,
without barriers such as reservoirs), small isolated populations that may now be comprised predominantly of adult individuals could be slowly dying out. Even given the very improbable absence of other anthropogenic threats, these disjunct populations could be lost simply due to the consequences of below-threshold effective population sizes. Because only 60 primarily disjunct streams among 162 historically occupied areas continue to harbor populations of the longsolid, and 65 primarily disjunct streams of 298 historically occupied areas continue to harbor populations of the round hickorynut, this is likely partial testimony to the principle of effective population size and its role in population loss.

The longsolid and round hickorynut exhibit several traits that influence population viability, including relatively small population size and low fecundity at many locations compared to other mussels (see Appendix A in Service 2018 and 2019). Small 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, small longsolid or round hickorynut populations may have reduced genetic diversity, be less genetically fit, and be more susceptible to disease during extreme environmental conditions compared to large populations (Frankham 1996, p. 1,505).

Genetic drift occurs in all species, but the lack of drift is more likely to negatively affect populations that have a smaller effective population size (number of breeding individuals) and populations that are geographically spread out and isolated from one another. Relatively low fecundity, commonly observed in species of
Fusconaia,
is another inherent factor that could influence population viability (Geist 2010, p. 91). Survival of juveniles in the wild is already low, and females produce fewer offspring than other mussel species (Haag and Staton 2003, p. 2,125). Factors such as low effective population size, genetic isolation, relatively low levels of fecundity and recruitment, and limited juvenile survival could all 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, based on our presumption of fish hosts of the longsolid and the known species of fish hosts for the round hickorynut, they are small-bodied fishes that have comparatively limited movement (Vaughn 2012, p. 6); therefore, natural expansion of longsolid and round hickorynut populations is limited.

Dendritic (branched) streams and rivers are highly susceptible to fragmentation and may result in multiple habitat fragments and isolated populations of variable size (Fagan 2002, p. 3,247). In contrast to landscapes where multiple routes of movement among patches are possible, pollution or other habitat degradation at specific points in dendritic landscapes can completely isolate portions of the system (Fagan 2002, p. 3,246).

Cumulative/Synergistic Effects

Populations that have a small effective population size (number of breeding individuals) and that are geographically spread out and isolated from one another are more vulnerable than more robust populations. Factors such as low effective population size, genetic isolation, relatively low levels of fecundity and recruitment, and limited juvenile survival could all 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). Impoundments result in the genetic isolation of mussel populations as well as fishes that act as hosts (Vaughn 2012, p. 6; Service 2018, pp. 59-60; Service 2019, p. 74). A culvert that is perched (
i.e.,
sitting above the downstream streambed) or improperly maintained at stream crossings can also act as barriers (Service 2018, pp. 50-54, 59-60; Service 2019, pp. 63, 90), and have similar effects as dams on stream systems. Fluctuating flows through a culvert can differ significantly from the rest of the stream, preventing fish passage and scouring downstream habitats.

Future Conditions

In the SSA reports, we forecast the longsolid's and round hickorynut's response to plausible future scenarios of environmental conditions and conservation efforts. The future scenarios project the threats into the future and consider the impacts those threats could have on the viability of the longsolid and round hickorynut. We apply the concepts of resiliency, redundancy, and representation to the future scenarios to describe possible future conditions of the longsolid and round hickorynut. The scenarios described in the SSA reports represent only three possible future conditions for each of the species. 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.

In the SSA reports, we considered three future scenarios. Scenario 1 assesses the species' response to factors influencing current longsolid and round hickorynut populations and management units, assuming the current level of impacts remain constant into the future. Scenario 2 assesses the species' response when factors that negatively influence most of the extant populations and management units are reduced by additional conservation, beyond the continued implementation of existing regulatory measures or voluntary conservation actions. Scenario 3 assesses the species' response to worsening conditions of the factors that most influence the species due to the implementation of known existing and projected development, resource extraction, hydroelectric projects, etc. An important assumption of the predictive analysis presented herein is that future population resiliency for each species is largely dependent on water quality, water flow, instream habitat conditions, and condition of riparian vegetation (see
Species Needs,
above).

The future conditions timeframe for our analysis is different for each species. A timeframe of 50 to 70 years into the future is evaluated for the longsolid, and 20 to 30 years into the future is evaluated for the round hickorynut. We selected these timeframes based on the availability of trends and threat information, planning documents, and climate modeling that could be reasonably projected into the future, and also the consideration of at least two generations for each species (
i.e.,
25 to 35 years for the long-lived longsolid, and on average 12-13 years (Shepard 2006, p. 7; Ehlo and Layzer 2014, p. 11) for the round hickorynut).

Longsolid

Our assessment predicts that if conditions remain the same or worsen into the future, all 60 populations would experience negative changes to the species' important habitat requisites (see
Species Needs,
above), including the loss of the single remaining population in the Cumberland River basin, and potentially resulting in no highly resilient populations (Scenario 3). Alternatively, the scenario that suggests additive conservation measures beyond those currently implemented (Scenario 2) could result in the continued persistence of all 60 populations in the future. However, we note that approximately 30 of 60 (50 percent) of these are currently low condition populations, based on either surveys that pre-date 2000 or on the collection of only five or fewer older, non-reproducing individuals. Some of these populations may already be extirpated. The risks facing the longsolid populations varied among scenarios and are summarized below (see Table 8-1 and Table ES-1 in the SSA report).

Under Scenario 1, lowered resiliency, representation, and redundancy are expected. Under this scenario, we predict that 1 population of the current 3 high condition populations would remain in high condition, 8 populations (13 percent) in medium condition, and 33 populations (55 percent) in low condition. Redundancy would be reduced with likely extirpation of 18 out of 60 (30 percent) currently extant populations; only the Ohio River basin (one of the three basins currently occupied by the species) would retain one highly resilient population (
i.e.,
the Green River population in the Upper Green management unit). Representation would be reduced, with two of the three currently occupied river basins continuing to harbor longsolid populations.

Under Scenario 2, we predict higher levels of resiliency in some areas of the longsolid's range than was estimated for Scenario 1; representation and redundancy would remain the same level as current conditions, with the species continuing to occur within all currently occupied management units and States across its range. Nine populations (15 percent) are predicted to be in high condition, compared to the current four populations in high condition. Scenario 2 also predicts 24 populations (40 percent) in medium condition and 27 populations (45 percent) in low condition; no populations would become extirpated. All three currently occupied major river

basins would remain occupied, and the existing levels of redundancy and representation would improve. It is possible that this scenario is the least likely to occur in the future as compared to Scenario 1 or 3 only because it will take many years (potentially beyond the 50- to 70-year timeframe analyzed in the SSA report) for all of the beneficial effects of management actions that are necessary to be implemented and realized on the landscape.

Under Scenario 3, we predict a significant decrease in resiliency, representation, and redundancy across the species' range. Redundancy would be reduced from three major river basins to two basins with no high condition populations remaining, and the likely extirpation of 44 (73 percent) of the currently extant populations. The resiliency of the remaining 16 populations is expected to be reduced to 3 populations (5 percent) in medium condition and 13 (22 percent) in low condition. In addition to the loss of 44 populations, 32 (29 percent) of the management units are predicted to become extirpated. Representation would be reduced to 13 management units, 2 major river basins, and 3 States (as compared to the current 9 States) occupied by the species.

Round Hickorynut

Our assessment predicts that if conditions remain the same (Scenario 1), 40 of 65 populations (62 percent) would experience negative changes to the important habitat requisites, including the potential loss of 23 populations. This includes the predicted extirpation of the two populations in the Cumberland River basin and the population in the Lower Mississippi River basin. Additionally, under Scenario 3, no highly resilient populations are able to persist, and 90 percent of remaining populations are in low condition. Alternatively, the scenario that suggests additive conservation measures beyond those currently implemented (Scenario 2) could result in the continued persistence of all 65 populations in the future. However, approximately 40 of 65 (62 percent) of these populations are currently in low condition. Many of the known populations of the round hickorynut have been collected as 10 or fewer individuals, with limited extent information available, due to the lack of survey effort targeting the species (Service 2019, Appendix A). The risks facing round hickorynut populations varied among scenarios and are summarized below (see also Table 8-1 and Table ES-1 in the SSA report).

Under Scenario 1, lowered resiliency, representation, and redundancy are expected. We predict that only one of the current four high condition populations would remain in high condition. Under this scenario, only the Great Lakes basin (one of the five basins currently occupied by the species) would retain a highly resilient population (
i.e.,
the Grand River). Of the 65 extant populations, 13 (20 percent) would be in medium condition and 28 (43 percent) would be in low condition. We estimate extirpation of 23 out of 65 (35 percent) populations. Redundancy would decline due to these population and management unit losses, resulting in a loss of the species from Pennsylvania and Mississippi. Representation would be reduced through extirpation of populations and management units in the Cumberland and Great Lakes basins, a 40 percent loss of redundancy compared to current conditions. Under this scenario, only three of the five currently occupied river basins (Great Lakes, Ohio, and Tennessee) continue to harbor round hickorynut populations.

Under Scenario 2, we predict higher levels of resiliency in some areas of the round hickorynut's range than is estimated for Scenario 1; representation and redundancy would remain the same level as current conditions with the species continuing to occur within all currently occupied management units and States across the species' 9-State range. Up to 15 populations (23 percent) are predicted to be high condition compared to the current 4 populations in high condition. Scenario 2 also predicts 37 populations (57 percent) in medium condition and 13 populations (20 percent) in low condition. All currently occupied major river basins would remain occupied, and the existing levels of redundancy and representation would improve. There are sufficient population sizes within each basin to facilitate augmentation and restoration efforts, whether it be within-basin translocations or captive propagation techniques. It is possible that this scenario is the least likely to occur in the future as compared to Scenario 1 or 3. This is because it will take many years (potentially beyond the 20- to 30-year time frame analyzed in the SSA report) for all of the beneficial effects of management actions that are necessary to be implemented on the landscape.

Under Scenario 3, we predict a significant decrease in resiliency, representation, and redundancy across the species' range. Redundancy would be reduced from five major river basins to three basins, with extirpations expected to occur in the Cumberland and Lower Mississippi River basins. No high condition populations would remain, and 46 (71 percent) of the 65 extant populations are likely to become extirpated. The resiliency of the remaining 19 populations is expected to be reduced to 2 populations (10 percent) in medium condition and 17 (90 percent) in low condition. In addition to the potential loss of 46 populations, 20 (59 percent) of the extant 34 management units are predicted to no longer harbor the species. Representation could be reduced to 14 management units across 3 major river basins. Extirpations are expected from the States of Pennsylvania, Michigan, and Mississippi, leaving 6 States (as compared to the current 9, and historically 12) occupied by the species.

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. Our assessment of the current and future conditions encompasses and incorporates the threats individually and cumulatively. Our current and future condition assessment is iterative because it 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.

Determination of Longsolid and Round Hickorynut Status

Introduction

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 “endangered species” or “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 a species meets the definition of “endangered species” or “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.

In conducting our status assessment of the longsolid and round hickorynut, we evaluated all identified threats under the Act's section 4(a)(1) factors and assessed how the cumulative impact of all threats acts on the viability of the species as a whole. That is, all the anticipated effects from both habitat-based and direct mortality-based threats are examined in total and then evaluated in the context of what those combined negative effects will mean to the future condition of the longsolid and round hickorynut. However, for the vast majority of potential threats, the effect on the longsolid and round hickorynut (
e.g.,
total losses of individual mussels or their habitat) cannot be quantified with available information. Instead, we use the best available information to gauge the magnitude of each individual threat on the longsolid and round hickorynut, and then assess how those effects combined (and as may be ameliorated by any existing regulatory mechanisms or conservation efforts) will impact the longsolid's or round hickorynut's future viability.

Longsolid—Status Throughout All of Its Range

After evaluating threats to the species and assessing the cumulative effect of the threats under the section 4(a)(1) factors, we determined that the species' distribution and abundance has been reduced across its range as demonstrated by both the number of occupied management units and the number of populations where it historically occurred. Historically, the species occurred within 162 populations and 105 management units across 12 States; currently, the species occurs in 60 populations and 45 management units across 9 States, which represents a 63 percent reduction of its historically occupied populations (although we note that the remaining populations are well-distributed as opposed to concentrated within its range). The conditions of the remaining 60 extant populations vary between being highly resilient, moderately resilient, or having low resiliency (see
Current Conditions
above, and section 5.2 in the SSA report (Service 2018, pp. 34-37)).

Currently, 3 populations (5 percent) are highly resilient, 9 (15 percent) are moderately resilient, and 48 (80 percent) have low resiliency. Although downward trends are evident compared to historical information, the 12 highly- to moderately-resilient populations continue to persist within three of the four major river basins the species is historically known to occupy. Current and ongoing threats from habitat degradation or loss (Factor A), residual impacts from past harvest and overutilization (Factor B), and invasive, nonnative species (Factor E) contribute to the species' negative effects associated with small population size (Factor E). The persistence of these 12 populations (in addition to some survey information) implies that recent recruitment is occurring in some populations to help maintain a level of resiliency, redundancy, and representation. Thus, after assessing the best available information, we conclude that the longsolid is not currently in danger of extinction throughout all of its range. We, therefore, proceed with determining whether the longsolid is likely to become endangered within the foreseeable future throughout all of its range.

At this point in time, and as noted above, the threats currently acting on the species include habitat degradation or loss from a variety of sources and invasive, nonnative species, all of which contribute to the negative effects associated with the species' small population size. Our analysis revealed that these threats are likely to continue into the foreseeable future, or approximately 30 to 50 years. This timeframe accounts for reasonable predictions of threats continuing into the future based on our examination of empirical data available over the last 30 years (
e.g.,
survey data, how threats are manifesting themselves on the landscape and the species, implementation of management plans and voluntary conservation actions), and also takes into consideration the biology of the species (multiple generations of a long-lived species) and the licensing schedules of dams within the species' range.

The best available information suggests that the threats currently acting upon the longsolid are expected to continue into the foreseeable future, some of which (
e.g.,
water quality and habitat degradation, and invasive, nonnative species) are reasonably expected to worsen over time, including concurrent with increasing human population trends and thus further reducing the species' resiliency, redundancy, and representation across its range. Our analysis reveals the potential for either none or a single population (
i.e.,
the Green River in Kentucky) to persist as highly resilient (
i.e.,
continued reproduction with varied age classes present) in the foreseeable future, assuming threats remain or worsen on the landscape. Additionally, the majority of the remaining populations would exhibit low resiliency, while many (between 30 and 73 percent of the current low condition populations) would potentially become extinct or functionally extinct (
e.g.,
significant habitat degradation, no reproduction due to highly isolated, non-recruiting individuals). Our future analysis also reveals a high risk that the species would become extirpated in one of the four historically occupied river basins (
i.e.,
Cumberland River basin); it has already been lost from the Great Lakes basin. Overall, the current threats acting on the species and its habitat are expected to continue, and there are no indications that these threats would lessen or that declining population trends would be reversed. Thus, after assessing the best available information, we conclude that the longsolid is likely to become in danger of extinction within the foreseeable future throughout all of its range.

Longsolid—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 signif

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Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A2020-17015. Public record. Not legal advice.