Endangered and Threatened Wildlife and Plants; Threatened Species Status for Pearl Darter, 43885-43896 [2017-20069]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 82, Number 181 (Wednesday, September 20, 2017)]
[Rules and Regulations]
[Pages 43885-43896]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2017-20069]


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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[Docket No. FWS-R4-ES-2016-0037; 4500030113]
RIN 1018-BB55


Endangered and Threatened Wildlife and Plants; Threatened Species 
Status for Pearl Darter

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Final rule.

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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), determine 
threatened species status under the Endangered Species Act of 1973 
(Act), as amended, for the pearl darter (Percina aurora), a fish whose 
historical range includes Mississippi and Louisiana. The effect of this 
regulation will be to add this species to the List of Endangered and 
Threatened Wildlife.

DATES: This rule becomes effective October 20, 2017.

ADDRESSES: This final rule is available on the internet at https://www.regulations.gov in Docket No. FWS-R4-ES-2016-0037 and on the 
Mississippi Field Office Web site at https://www.fws.gov/mississippiES/. Comments and materials we received, as well as 
supporting documentation we used in preparing this rule, are available 
for public inspection at https://www.regulations.gov and by appointment, 
during normal business hours at: U.S. Fish and Wildlife Service, 
Mississippi Ecological Services Field Office, 6578 Dogwood View 
Parkway, Jackson, Mississippi 39213, by telephone 601-321-1122 or by 
facsimile 601-965- 4340.

FOR FURTHER INFORMATION CONTACT: Stephen Ricks, Field Supervisor, U.S. 
Fish and Wildlife Service, Mississippi Ecological Services Field 
Office, 601-321-1122. Persons who use a telecommunications device for 
the deaf (TDD) may call the Federal Relay Service at 800-877-8339.

SUPPLEMENTARY INFORMATION: 

Executive Summary

    Why we need to publish a rule. Under the Endangered Species Act of 
1973, as amended (Act, 16 U.S.C. 1531 et seq.), if we determine that a 
species is an endangered or threatened species throughout all or a 
significant portion of its range, we are required to promptly publish a 
proposal in the Federal Register and make a determination on our 
proposal within 1 year. Listing a species as an endangered or 
threatened species can only be completed by issuing a rule. We 
published a proposed rule to add the pearl darter (Percina aurora) to 
the List of Endangered and Threatened Wildlife in title 50 of the Code 
of Federal Regulations (50 CFR 17.11(h)) as threatened on September 21, 
2016 (81 FR 64857).
    What this document does. This rule will finalize the listing of the 
pearl darter as a threatened species.
    The basis for our action. Under the Act, we may determine that a 
species is an endangered or threatened species based on 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

[[Page 43886]]

existing regulatory mechanisms; or (E) other natural or manmade factors 
affecting its continued existence. We have determined that water 
quality decline from point and nonpoint source pollution continues to 
impact portions of this species' habitat. In addition, geomorphology 
changes attributed to historical sand and gravel mining operations 
within the drainage are considered an ongoing threat. This species has 
been extirpated from the Pearl River watershed and is confined today to 
the Pascagoula River basin where the species' small population size, 
scattered locations, and low genetic (allelic) diversity increase its 
vulnerability to extirpation from catastrophic events.
    Peer review and public comment. We sought comments from independent 
specialists to ensure that our determination was based on 
scientifically sound data, assumptions, and analyses. We invited these 
peer reviewers to comment on our listing proposal. We also considered 
all comments and information received from the public during the 
comment period.

Previous Federal Action

    Please refer to the September 21, 2016, proposed listing rule (81 
FR 64857) for a detailed description of previous Federal actions 
concerning this species.

Background

    For a more detailed discussion of the taxonomy, biology, status, 
and threats affecting the species, please refer to the proposed listing 
rule. In the proposed rule, we evaluated the biological status of the 
species and factors affecting its continued existence. Our assessment 
was based upon the best available scientific and commercial data on the 
status of the species, including past, present, and future threats.

Summary of Comments and Recommendations

    In the proposed rule, we requested that all interested parties 
submit written comments on the proposal by November 21, 2016. We also 
contacted appropriate Federal and State agencies, scientific experts 
and organizations, and other interested parties and invited them to 
comment on the proposal. Newspaper notices inviting general public 
comment were published in the Hattiesburg American, Mississippi Press, 
and Clarion-Ledger on October 2, 2016. We did not receive any requests 
for a public hearing. All substantive information provided during the 
comment period has either been incorporated directly into this final 
determination or is addressed in the more specific response to comments 
below.

Peer Reviewer Comments

    In accordance with our peer review policy published on July 1, 1994 
(59 FR 34270), we solicited expert opinion from three individuals with 
scientific expertise that included familiarity with pearl darter and 
its habitat, biological needs, and threats. We received responses from 
all three of the peer reviewers.
    We reviewed all comments received from the peer reviewers for new 
substantive information regarding the listing of the pearl darter. The 
peer reviewers generally concurred with our methods and conclusions and 
provided additional information, clarifications, and suggestions to 
improve the final rule. Where appropriate, we incorporated new 
information into the final rule as a result of the peer reviewer 
comments, including new survey information. Other substantive peer 
reviewer comments are below.
    (1) Comment: One peer reviewer suggested our statement that the 
species was extirpated from the Pearl River drainage was premature, 
since surveys in that system were ongoing, and cautioned that a final 
listing decision should be withheld until surveys were completed.
    Our Response: While upper Pearl River basin surveys for the pearl 
darter were completed in 2011 (Schaefer and Mickle 2011), surveys for 
the darter in the lower Pearl River drainage were only completed by the 
Mississippi Department of Wildlife, Fisheries, and Parks in May of 2017 
(Wagner et al. 2017, entire). Those surveys, which included both 
traditional surveys and eDNA analysis (Wagner et al. 2017, p. 5), were 
utilized over the last 2 years in an attempt to locate evidence of this 
species persisting in the Pearl River system. Our determination that 
the pearl darter has not been collected from the Pearl River drainage 
in over 40 years, and is considered extirpated from this system, is 
validated by these recent survey results.
    (2) Comment: One peer reviewer stated that pulp mills should be 
considered a threat to water quality degradation. The reviewer also 
expressed a suspicion that pulp mill effluent may have had some 
influence on extirpation of pearl darters in the Pearl River.
    Our Response: We agree and have made changes to this final rule to 
reflect the peer reviewer's input in the Summary of Factors Affecting 
the Species section, below.
    (3) Comment: One peer reviewer stated that increased demand for 
water withdrawal by industry and municipalities should be considered an 
additional threat to the species in the Pascagoula drainage. The 
reviewer stated that this activity will be a continuing threat for all 
aquatic resources as coastal populations grow and industrial needs 
expand. The commenter cited the 2006 proposed Richton Salt Dome as an 
example of water withdrawal posing a threat to the pearl darter.
    Our Response: We agree that water withdrawal from the Pascagoula 
drainages could have an impact on the ecological health of the system 
and potentially impact the pearl darter. However, at this time, we have 
no information to indicate that increased demand for water withdrawal 
by industry and municipalities currently poses a threat to the pearl 
darter, and we note that the peer reviewer did not identify any 
specific active projects. The Richton Salt Dome project cited by the 
peer reviewer, which at one time was a concern, was terminated and 
removed from the Department of Energy's budget in 2011.
    (4) Comment: One peer reviewer stated that there was no information 
to indicate there has been a decline in pearl darter abundance in the 
Bouie River and Black Creek and, particularly, no information 
attributing any declines to sedimentation and unstable banks. These 
areas have historically had few specimens of darter and have not been 
thoroughly surveyed.
    Our Response: We agree that there are inadequate data and a lack of 
thorough surveying of the Bouie River and Black Creek to definitively 
note a decline of the species in those systems, and we have clarified 
the rule accordingly. Until recently, there had been no collection 
efforts in the Bouie River and Black Creek since 2000. However, in 
2016-2017, survey efforts in these systems found pearl darters to be 
sparsely present in a few sites (Schaefer in litt. 2017). Evidence of 
substantial sedimentation and unstable banks in the Bouie River and 
Black Creek has been documented in the past (Mossa and Coley 2004, p. 
7; Mississippi Department of Environmental Quality 2005c, p. 16) and 
observed currently (Schaefer in litt. 2017). The negative impact of 
excessive sedimentation on darter distribution is well known and 
addressed under Factor A in the Summary of Factors Affecting the 
Species section of the preamble to this rule. Furthermore, there are 
also likely other factors contributing to water quality degradation in 
these systems,

[[Page 43887]]

such as point and nonpoint source pollution related to stormwater 
runoff and effluent discharge from industry, agriculture, and 
urbanization; therefore, we have revised our statement regarding 
sedimentation.
    (5) Comment: One peer reviewer commented that our statement in the 
proposed rule on low genetic diversity and restricted gene flow as 
reported by Kreiser et al. (2012) ran counter to the hypothesized long-
distance spawning migrations noted elsewhere in the rule. The commenter 
stated that the genetic data support a series of potentially disjunct 
populations rather than one contiguous population.
    Our Response: We appreciate the comment and have clarified in this 
final listing rule the statement that pearl darters may have long-
distance spawning migrations (Bart et al. 2001, p. 14). Kreiser's (et 
al. 2012, pp. 14-17) recent genetic studies, indicating a series of 
potentially disjunct populations, are likely a more accurate 
representation of the population structure of the pearl darter (see 
Summary of Factors Affecting the Species, Factor E).

Comments From States

    The proposed rule was reviewed by the Mississippi Department of 
Wildlife, Fisheries and Parks; the Mississippi Forestry Commission; and 
the Louisiana Department of Wildlife and Fisheries. The individual 
associated with the Mississippi Department of Wildlife, Fisheries and 
Parks also served as a peer reviewer, and his comment is addressed in 
Comment 1 above. The State agencies generally concurred with our 
methods and commented that the literature and data were thorough and 
properly documented. They stated that we should withhold our final 
listing decision until their surveys in the Pearl River drainage had 
been completed. Mississippi Department of Wildlife, Fisheries and Parks 
recently provided additional information from their recent site 
surveys. The Louisiana Department of Wildlife and Fisheries agreed that 
there were no recent records from the Pearl River system despite recent 
sampling efforts. An issue raised by the Mississippi Forestry 
Commission is addressed below.
    (6) Comment: The Mississippi Forestry Commission and two commenters 
from the timber industry stated that we mischaracterized the use of 
best management practices (BMPs) in Mississippi by stating that: (1) 
Their use was confined to lands managed by The Nature Conservancy and 
the State of Mississippi, and (2) the lack of a mandatory requirement 
makes forestry BMPs less effective. The commenters pointed out that the 
forest industry has a number of forest certification programs, such as 
the Sustainable Forestry Initiative, which require participating 
landowners to meet or exceed State forestry BMPs. The commenters also 
stated that silviculture practices implemented with BMPs have minimal 
impacts on aquatic species, and that a recent statewide monitoring 
survey by Mississippi Forestry Commission indicated that BMPs are being 
implemented across all silviculture landscapes in Mississippi 
regardless of ownership.
    Our Response: We appreciate the additional information provided by 
the commenters and commend the timber industry and landowners on their 
implementation of BMPs in their timber operations and also the success 
of forestry certification programs, such as Sustainable Forestry 
Initiative. We have updated information in this rule to acknowledge the 
contribution of these forest landowners implementing BMPs in the 
Summary of Factors Affecting the Species section, below.

Public Comments

    We received five comments from the public, two of which are 
addressed in Comment 6, above; the three other commenters simply 
expressed their support for the proposed listing.

Summary of Changes From the Proposed Rule

    This final rule incorporates minor changes to our proposed rule 
based on the comments we received, as discussed above in Summary of 
Comments and Recommendations, and newly available survey information. 
The survey data allowed us to refine distribution information; thus, 
the final total current range of the species is different from that in 
the proposed rule. Many small, nonsubstantive changes and corrections 
were made throughout the document in response to comments (e.g., 
updating the Background section, threats, minor clarifications). 
However, the information we received in response to the proposed rule 
did not change our determination that the pearl darter is a threatened 
species, nor was it significant enough to warrant reopening the public 
comment period. Below is a summary of substantive changes made to the 
final rule.
     We now estimate the total current range of the pearl 
darter in the Pascagoula watershed to be 668 kilometers (km) (415 miles 
(mi)) based on a reanalysis of collection records and recent survey 
results. Detailed information about the species' range within each of 
the seven river/creek systems is presented in the preamble of this 
rule, under Current Distribution.
     Additional information on habitat and population structure 
from peer reviewers and recent studies (Wagner et al. 2017) has been 
added to the preamble.
     Additional information and suggestions from peer reviewers 
was added to clarify and improve the accuracy of the information in the 
Distribution, Habitat, Biology, and Threats sections of the preamble to 
the proposed rule.
     Additional information on the species' abundance and 
probable cause of decline in the Pearl River, as related to the 
potential threat to existing populations in the Pascagoula system, from 
two peer reviewers was added into the Summary of Factors Affecting the 
Species section of this rule, below.
     Additional narrative on historical threats within the 
Pearl River basin, as well as additional historical and current threats 
affecting water quality within the Pascagoula River basin, including 
increased brine concentration from oil and gas production and pulp mill 
effluent related to pulp, paper, and lumber mills, was added to the 
preamble.

Summary of Biological Status

    Below we present a summary of the biological and distributional 
information discussed in the proposed listing rule (81 FR 64857; 
September 21, 2016). We also present new information published or 
obtained since the proposed rule was published (see Summary of Changes 
from the Proposed Rule, above).

Taxonomy and Species Description

    The pearl darter (Percina aurora) is a small fish and is one of 
three members of the subgenus Cottogaster (Ross 2001, p. 500). The 
species is allied to the channel darter (P. copelandi) (Ross et al. 
1989, p. 25) but is distinguished from it by its larger size, lack of 
tubercules (small, raised, skin structures), heavy pigmentation, number 
of marginal spines on belly scales of breeding males, and fully scaled 
cheeks (Suttkus et al. 1994, pp. 13-14). Generally, pearl darters range 
in size from 22 to 59 millimeters (mm) (0.87 to 2.3 inches (in)) in 
length with the majority of adults being from 30 to 41 mm (1.2 to 1.6 
in) long (Clark and Schaefer 2015, p. 10).

Historical Distribution

    The pearl darter is historically known from localized sites within 
the Pearl and Pascagoula River drainages in

[[Page 43888]]

Mississippi and Louisiana, based on collection records from 16 counties 
and parishes of Mississippi and Louisiana. Examination of site records 
of museum fish collections from the Pearl River drainage (compiled from 
Suttkus et al. 1994, pp. 15-18) suggests that the pearl darter once 
inhabited the large tributaries and main channel habitats within these 
drainages from St. Tammany Parish, Louisiana, to Simpson County, 
Mississippi. This area totaled approximately 708 km (440 mi) within the 
Pearl River basin and included the lower Pearl River, the Strong River, 
and the Bogue Chitto River (compiled from MMNS 2016, unpublished data; 
Slack et al. 2005, pp. 5-10; Ross 2001, p. 499; Ross et al. 2000, pp. 
2-5; Bart and Piller 1997, pp. 3-10; Bart and Suttkus 1996, pp. 3-4; 
Suttkus et al. 1994, pp. 15-18). However, there have been no records of 
this species from the Pearl River drainage in over 40 years, despite 
repeated collecting efforts through the years (Wagner et al. 2017, pp. 
3-10, 12; Geheber and Piller 2012, pp. 633-636; Schaefer and Mickel 
2011, p. 10; Slack et al. 2005, pp. 5-10; Tipton et al. 2004, pp. 56-
57; Ross 2001, p. 499; Bart and Piller 1997, p. 1; Bart and Suttkus 
1996, pp. 3-4; Bart and Suttkus 1995, pp. 13-14; Suttkus et al. 1994, 
pp. 15-18). Survey efforts over the last few years at all historical 
sites, including north of and just below the Ross Barnett Reservoir 
(Schaefer and Mickle 2011, pp. 8-10), have confirmed its absence from 
the Pearl River system (Wagner et al. 2017, pp. 3-4; Roberts in litt. 
2015; Geheber and Piller 2012, p. 633), including the recent analysis 
of water samples for eDNA from the Pearl River proper, Strong River, 
and Bogue Chitto River (Piller in litt. 2017). Thus, the pearl darter 
is considered extirpated from the Pearl River system today.

Current Distribution

    Today, the pearl darter occurs in scattered sites within an 
approximately 668-km (415-mi) area of the Pascagoula drainage, 
including the Pascagoula (101 km, 63 mi), Chickasawhay (257 km, 160 
mi), Leaf (186 km, 115 mi), Chunky (31 km, 19 mi), and Bouie (24 km, 15 
mi) Rivers and Okatoma (37 km, 23 mi) and Black Creeks (32 km, 20 mi) 
(Wagner et al. 2017, pp. 3-10, 12; Wagner in litt. 2017; Clark and 
Schaefer 2015, pp. 10, 19, 23; Schaefer and Mickle 2011, pp. 1-3; Slack 
et al. 2002, p. 9).
    The average catch at known occupied sites, using standard sampling 
(30 minutes with heavy leaded seine) is 2.1 individuals (Wagner et al. 
2017. pp. 3-4; Clark and Schaefer 2015, pp. 9-14, 18-22), indicating a 
species that is rare. Surveys by Kreiser et al. (2012, pp. 29-32) found 
sporadic occurrences of the species within the Pascagoula River from 
its headwaters at the confluence of the Leaf and Chickasawhay Rivers 
downstream to where the river bifurcates (splits). Recent survey 
efforts indicate reproducing populations in the Chickasawhay and Leaf 
Rivers, based on the presence of different size classes (Clark in litt. 
2017; Wagner in litt. 2017; Wagner et al. 2017, p. 3; Schaefer in litt. 
2017; Clark and Schaefer 2015, pp. 9-14, 18-22). Though there is a 
clear pattern of higher abundance and greater rate of occurrence at 
sites in the Chickasawhay River (5.03  0.62 pearl darters 
per hour) compared to the Leaf River (2.18  0.56 pearl 
darters per hour); a pattern that has remained constant over time 
(Clark and Schaefer 2015, pp. 9-14). Surveys in 2016 of historical 
locations (Clark in litt. 2017; Schaefer in litt. 2017) in the Bouie 
River, Okatoma Creek, and Black Creek yielded seven fish in the Okatoma 
Creek and one specimen each in the Bouie River and Black Creek. In 
2017, one pearl darter was collected in the Chunky River, confirming 
its presence in that system for the first time since its last 
collection there over 15 years ago.

Habitat and Biology

    The pearl darter occurs in low-gradient, coastal plain rivers and 
creeks (Suttkus et al. 1994, p. 13), predominately classified as 4th to 
2nd order streams (Strahler stream order hierarchy). There have been no 
comprehensive microhabitat studies on the pearl darter; however, based 
on observations of occupancy in the field, microhabitat features 
consist of a bottom substrate mixture of sand, silt, loose clay, 
gravel, organic material, and snags (Slack et al. 2005, pp. 9-11). The 
species has been collected at the steep ends of sandbars, and inside 
river bends where material is deposited. The water where the species is 
typically captured has a slow to medium current velocity (0.003 to 
0.635 centimeters/second (cm/s) (0.53 to 0.25 in/s) (tabulated from 
Clark in litt. 2017, Slack in litt. 2017, Schaefer in litt. 2017, 
unpublished data; Slack et al. 2005, p. 10). In fact, based on cluster 
analysis and ordination of habitat data of the Leaf and Chickasawhay 
Rivers, higher densities of pearl darters were found in slower moving, 
deeper waters with finer substrate (Clark and Schaefer 2015, p. 11). 
There is very little aquatic vegetation in these drainages (Slack et 
al. 2005, p. 9), and vegetation that may be present is usually river 
weed (Podostemum ceratophyllum) attached to rocks (Drennen and Wagner 
2017, pers. observ.). Banksides where the pearl darter was collected 
are vegetative and not vertical or severely eroded (Schaefer in litt. 
2017, unpublished data).
    There is no specific information available on the diet of the pearl 
darter. However, the channel darter (P. copelendi), a closely allied 
species in similar habitat, has been reported to feed on chironomid 
flies, small crustaceans, mayflies, and caddisflies (Kuehne and Barbour 
1983, p. 49).

Summary of Factors Affecting the Species

    Below we present a summary of the threats information from the 
proposed listing rule. We also present new information published or 
obtained since the proposed rule was published, including information 
received during the public comment period.

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

    Members of the Cottogaster subgenus have undergone range 
contractions that are of potential conservation concern throughout 
their respective distributions (Dugo et al. 2008, p. 3; Warren et al. 
2000, pp. 7-8; Goodchild 1994, pp. 433-435). The pearl darter was 
extirpated from the Pearl River drainage, perhaps as early as the 
1970s, and many of the stressors thought to have played a role in its 
loss in that system are present in the Pascagoula River drainages where 
the species occurs today, including impoundments (sills and dams); 
instability in the channel; increased sedimentation from the removal of 
riparian vegetation and poor agriculture and silviculture practices; 
and general chronic water degradation from point and non-point source 
pollution (Piller et al. 2004, pp. 1004-1011; TNC 2004, p. 5; Ross 
2001, pp. 499-500).
Water Quality Degradation
    Water quality degradation, particularly non-point source pollution 
from incompatible commercial and industrial development and land use 
practices, has been a major concern within the Pearl River basin (TNC 
2004, p. 18). Similarly, the Pascagoula River system suffers from acute 
and localized water quality degradation by nonpoint source pollution in 
association with surface, stormwater, and effluent runoffs from 
urbanization and municipal areas (MDEQ 2005c, p. 23; 2005d, p. 16). 
``Total Maximum Daily Loads'' (TMDLs), a term in the U.S. Clean Water 
Act describing a benchmark set for a certain pollutant to bring water 
quality up to the applicable standard, have been established for 89 
segments of the Pascagoula River basin, many of which

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include portions of the pearl darter's range (MDEQ 2014a, pp. 18-21). 
For sediment, one of the most pervasive pollutants, the State of 
Mississippi has TMDLs for various tributaries and main stems of the 
Leaf and Chickasawhay Rivers. To date, efforts by the State of 
Mississippi to improve water quality in the Pascagoula River basin to 
meet these TMDL benchmarks have been inadequate (MDEQ 2014a, pp. 18-
21). Thirty-nine percent of the Pascagoula River basin tributaries are 
rated fair or poor due to pollution impacts (MDEQ 2014a, pp. 18-21; 
MDEQ 2008, p. 17).
    Most water quality threats are due to increased sediment loads and 
variations in pH (MDEQ 2014a, pp. 1-51; 2008a, pp. 13-15). Sediment in 
stormwater runoff increases water turbidity and temperature and 
originates locally from poorly maintained construction sites, timber 
harvest tracts, agricultural fields, clearing of riparian vegetation, 
and gravel extraction in the river floodplain. Suttkus et al. (1994, p. 
19) attributed the loss of the pearl darter in the Pearl River to 
increasing sedimentation from habitat modification caused by the 
removal of riparian vegetation and extensive cultivation near the 
river's edge. Excessive sediments disrupt feeding and spawning of fish 
and aquatic insects, abrade and suffocate periphyton (mixture of algae, 
bacteria, microbes, and detritus that is attached to submerged 
surfaces), and impact fish growth, survival, and reproduction (Waters 
1995, pp. 55-62). A localized portion of the Chickasawhay River is on 
the State Section 303(d) List of Water Bodies as impaired due to 
sediment (MDEQ 2005b, p. 17).
    Nonpoint source pollution is a localized threat to the pearl darter 
within the drainage, and is more prevalent in areas where certified 
best management practices (BMPs) are not utilized. The use of certified 
BMPs during land-altering activities can greatly reduce impacts to 
water quality. Certified BMPs, currently implemented by the forestry 
industry (e.g., Sustainable Forestry Initiative, Forest Stewardship 
Council, and American Tree Farm System), are helping to minimize or 
eliminate non-point source pollution during the course of forestry 
activities. The Mississippi Forestry Commission (2016, entire) reports 
certified BMP implementation rates to be high in Mississippi for 
forestry activities, primarily due to the efforts of State forestry 
agencies and forest certification programs (Schilling and Wigley 2015, 
pp. 3-7).
    Historically, timber harvesting and processing was extensive in the 
Pearl River basin, and at one time, the basin was home to one of the 
most important lumber centers in the United States (Thigpen 1965, pp. 
66-69). Pulp and paper manufacturing began in the Pascagoula watershed 
in Mississippi with three major mills (Monthly Review 1958, p. 83). 
Today, there are six major pulp mills in the Pascagoula River basin 
whose effluent may be a threat to the pearl darter. Paper mill effluent 
is a contributor to water quality degradation and is suspected to have 
had some influence on the extirpation of the pearl darter in the Pearl 
River system (Slack in litt. 2016). Fish and mussel kills were 
reportedly not uncommon within reaches downstream from pulp mills in 
Lawrence County near historical locations for the pearl darter (Slack 
in litt. 2016). As recently as 2011, a ``black liquor'' (wastewater) 
spill from a paper manufacturing process resulted in a massive fish 
kill in the Pearl River (Kizha et al. 2016, pp. 926-929; Piller and 
Geheber 2015, pp. 2433-2434).
    Numerous studies have documented the effects of pulp and paper mill 
effluents on fish populations (Beyer et al. 1996, pp. 212-224). 
Depending on the bleaching process, pulp- and paper mill effluents may 
contain various kinds and concentrations of chlorinated organic 
compounds such as polychlorinated dibenzodioxins (dioxins) and 
polychlorinated dibenzofurans (furans), which elicit several lethal and 
sublethal effects in fish, such as alterations in steroid biosynthesis 
(manufacturing of hormones and other organic compounds), gonadal (sex 
gland) development, sexual maturation, and expression of secondary sex 
characteristics (features that appear at maturity such as coloration). 
These types of compounds are known to bioaccumulate and have 
reproductive and antiestrogen (opposite effects of hormones) impacts on 
fish (Hoffman et al. 2003, pp. 1063-1065).
    Additionally, some contaminants may bind with one another (i.e., 
heavy metals bind with sediments or other contaminants in the water 
column) within the Pascagoula River drainage. These bound chemical 
contaminants have not been addressed in TMDLs. Only seven TMDLs for 
metals have been completed (MDEQ 2008, pp. 1-55). The Davis Dead River, 
a tributary at the most downstream site of the pearl darter's range, is 
considered critically impaired by mercury (MDEQ 2011, pp. 1-29), and 
fish consumption advisories continue for mercury in certain gamefish 
species in the Pascagoula River main stem (MDEQ 2008, p. 43).
    There are 15 permitted point source discharge sites within the 
Bouie River system (MDEQ 2005a, p. 6) and an unknown amount of nonpoint 
runoff sites. Municipal and industrial discharges during periods of low 
flow (i.e., no or few rain events) intensify water quality degradation 
by increasing water temperatures, lowering dissolved oxygen, and 
changing pH. Within the Pascagoula River basin, pollutants causing 
specific channel or river reach impairment (i.e., those pollutants 
preventing the water body from reaching its applicable water quality 
standard (Environmental Protection Agency 2012, pp. 1-9)), include 
sedimentation; chemicals and nutrients in the water column; and various 
toxins, such as heavy metals like lead or cadmium for a total of 304 km 
(189 mi) impaired riverine segments. TMDLs were completed for 
pesticides such as dichlorodiphenyltrichloroethane (DDT), toxaphene, 
dioxin, and pentachlorophenol, although much of the data and results 
are not finalized and remain unavailable for the designated reaches 
(Environmental Protection Agency 2012, pp. 1-7; MDEQ 2003, pp. 5-10; 
Justus et al. 1999, p. 1).
    Localized wastewater effluent into the Leaf River from the City of 
Hattiesburg is negatively impacting water quality (Hattiesburg American 
2015, pp. 1-2; Mississippi River Collaboration 2014, p. 1). Existing 
housing, recreational cabins, and trailers along the banks of the Leaf 
River between I-59 and the town of Estabutchie cause nutrient loading 
through treated sewage and septic water effluent (Mississippi River 
Collaboration 2014, p. 1). In 1997, Bart and Piller (p. 12) noted 
extensive algal growth during warmer months in the Leaf and Bouie 
Rivers, indicating nutrient and organic enrichment and decreases in 
dissolved oxygen and pH changes. Today, at specific locations, the 
water quality of the Bouie and Leaf Rivers and their tributaries 
continues to be negatively impacted by sediment, organic enrichment, 
low dissolved oxygen, fecal coliform, and elevated nutrients (MDEQ 
2016, p. 86, 91; 2014a, p. 18, 21, 32; 2005a, pp. 1-26; 2004, pp. 1-
29).
Oil and Gas Development
    Nonpoint and point source pollution from oil and gas exploration, 
including drill field construction, active drilling, and pipeline 
easements, may add localized pollutants into the Pascagoula River basin 
during stormwater runoff events if BMPs are not used. There is one 
major oil refinery within the basin along with 6 oil pumping stations, 
10 major crude pipelines, 4 major product oil pipelines, and 5 major 
gas and more than 25 lesser gas lines stretching hundreds of miles and 
crisscrossing the

[[Page 43890]]

main stem Pascagoula, Bouie, Leaf, Chickasawhay, and Chunky Rivers and 
their tributaries; in addition, there are more than 100 active oil 
producing wells within the pearl darters' watersheds (compiled from Oil 
and Gas Map of Mississippi in Phillips 2013, pp. 10, 23). All have the 
potential to rupture or leak and cause environmental and organismal 
damage as evidenced by the Genesis Oil Company and Leaf River oil spill 
of 2000 (Environmental Science Services, Inc. 2000, pp. 1-50; Kemp 
Associates, PA, 2000, pp. 4-5; The Clarion-Ledger, December 23, 1999, 
p. 1B) and Genesis Oil Company spill in Okatoma Creek in February 2016 
(Drennen 2016, pers. observ.). In addition to gas pipelines, there are 
numerous railways that cross pearl darter habitat that are subject to 
accidental and catastrophic spilling of toxins such as fuel oil, 
methanol, resin, and fertilizer (MDEQ 2014b, pp. 1-23).
    Alternative oil and gas collection methods (i.e., hydraulic 
fracturing (``fracking'') and horizontal drilling and injection) have 
allowed the expansion of oil and gas drilling into deposits that were 
previously inaccessible (Phillips 2013, p. 21), which has led to 
increased activity within southern Mississippi, including portions of 
the Pascagoula River basin. There are more than 100 water injection 
disposal wells and enhanced oil recovery wells within the basin 
(compiled from Active Injection Well Map of Mississippi in Phillips 
2013, p. 49). A variety of chemicals (e.g., 15% diluted hydrochloric 
acid, surfactants, potassium chloride) are used during the drilling and 
fracking process (Colborn et al. 2011, pp. 1040-1042), and their wastes 
are stored in open pits (retention basins) or storage facilities. 
Spills during transport or releases due to retention basin failure or 
overflow pose a risk for surface and groundwater contamination, which 
can cause significant adverse effects to water quality and aquatic 
organisms that inhabit these watersheds (Osborn et al. 2011, pp. 8172-
8176; Kargbo et al. 2010, pp. 5680-5681; Wiseman 2009, pp. 127-142). In 
addition, contamination of streams with brine (chloride), a byproduct 
of oil and gas development, poses a significant risk to aquatic 
habitats and species. High chloride concentrations interfere with 
osmoregulation (maintenance of proper levels of salts and other solutes 
in bodily fluids) and hinder the organism's survival, growth, and 
reproduction (Hunt et al. 2012, p. 1). Brine contamination has been 
documented within the pearl darter's historical range in the Pearl 
River system (Kalhoff 1993, pp. 12-15, 19-20, 25; Kalhoff 1986, p. 49) 
and within the Pascagoula River basin where it currently occurs, 
including several Leaf and Chickasawhay River drainage basin 
tributaries (Kalhoff 1986, pp. 52-63). There is currently no routine 
water quality monitoring in areas where the pearl darter currently 
occurs, so it is unlikely that the effects of a leak or spill would be 
detected quickly enough to allow for a timely response.
Geomorphology Changes
    Piller et al. (2004, pp. 1004-1011) cited numerous human-caused 
disturbances within the Pearl River since the 1950s, including 
channelization, reservoir construction, and channel modification from 
bank collapse downstream of dams. Specifically, the Pearl River 
Navigation Canal in 1956, the Ross Barnett Reservoir in 1964, and 
channel changes of the lower Pearl River (increased width and decreased 
depth) were implicated in the decline of abundance for several fish 
species in that system (Piller et al. 2004, pp. 1004-1011). These 
habitat modifications and channel changes resulted in the loss of 
gravel substrates in places, completely replacing gravel bars with sand 
or sediment, which are not appropriate substrate for the pearl darter 
and other species (Tipton et al. 2004, pp. 58-60; TNC 2004, p. 5). 
Tipton et al. (2004, pp. 58-60) documented a decrease in fish diversity 
and abundance within the disturbed reaches as compared with relatively 
undisturbed reaches. These changes most likely contributed to the 
decline of the pearl darter in the Pearl River system and potentially 
threaten the species in the Pascagoula system.
    Pearl darters are not found in impounded waters and are intolerant 
of lentic (standing water) habitats that may be formed by gravel mining 
or other landscape-altering practices. Incompatible sand and gravel 
mining and its disruption of topography, vegetation, and flow pattern 
of streams is considered a major stressor to the Pearl River system 
where the pearl darter once occurred (TNC 2004, p. 16). In the species' 
current range in the Pascagoula system, the results of historical sand 
and gravel dredging impacts have been a concern for the Bouie and Leaf 
Rivers (MDEQ 2000, pp. 1-98). Historically, the American Sand and 
Gravel Company (1995, p. B4) has mined sand and gravel using a 
hydraulic suction dredge, operating within the banks or adjacent to the 
Bouie and Leaf Rivers. Large gravel bars of the river and its 
floodplain have been removed over the past 50 years, creating open-
water areas that function as deep lake systems (American Sand and 
Gravel Company 1995, pp. B4-B8). The creation of these large, open-
water areas has accelerated geomorphic processes, specifically 
headcutting (erosional feature causing an abrupt drop in the streambed) 
that has adversely affected the flora and fauna of many coastal plain 
streams (Patrick et al. 1993, p. 90). Mining in active river channels 
typically results in incision upstream of the mine by knickpoints 
(breaks in the slope of a river or stream profile caused by renewed 
erosion attributed to a bottom disturbance that may retreat upstream), 
sediment deposition downstream, and an alteration in channel morphology 
that can have impacts for years (Mossa and Coley 2004, pp. 1-20). The 
upstream migration of knickpoints, or headcutting, may cause 
undermining of structures, lowering of alluvial water tables (aquifer 
comprising unconsolidated materials deposited by water and typically 
adjacent to rivers), channel destabilization and widening, and loss of 
aquatic and riparian habitat. This geomorphic change may cause the 
extirpation of riparian and lotic (flowing water) species (Patrick et 
al. 1993, p. 96).
    Sedimentation from unstable banks and loose, unconsolidated 
streambeds (Bart and Piller 1997, p. 12) is likely impacting the pearl 
darters in the Bouie River and Black Creek. Mossa and Coley (2004, p. 
17) determined that, of the major tributaries in the Pascagoula basin, 
the Bouie River was the least stable. Channel enlargement of the Bouie 
River showed higher than background values associated with avulsions 
(the rapid abandonment of a river channel and the formation of a new 
river channel) into floodplain pits and increased sedimentation. In 
addition, channel enlargement of 400 to 500 percent in the Bouie River 
has occurred at specific sites due to instream gravel mining (Mossa et 
al. 2006, entire; Mossa and Coley 2004, p. 17). Ayers (2014, pp. 43-45) 
also found significant and lengthy instream channel form changes in the 
Chickasawhay River floodplain. Clark and Schaefer (2015, pp. 13-14) 
noted a slight decrease in fish species richness in the upper 
Pascagoula River basin from their 2004 sampling, which they attributed 
to past anthropogenic influences such as gravel mining, bankside 
practices, and construction.
    In the Bogue Chitto River of the Pearl River basin, Stewart et al. 
(2005, pp. 268-270) found that the assemblages of fishes had shifted 
over 27 years. In this time period, the sedimentation rates

[[Page 43891]]

within the system had increased dramatically and caused the decrease in 
the relative abundance of all fish in the family Percidae (Stewart et 
al. 2005, pp. 268-270) from 35 percent to 9 percent, including the 
extirpation of pearl darters. Ross et al. (1992, pp. 8-9) studied 
threats to the Okatoma Creek (Pascagoula basin) fish diversity and 
predicted that geomorphic changes to the stream would reduce the fish 
habitat diversity resulting in a decline of the fish assemblages, 
including the pearl darter.
Impoundments
    Dams and other flow control structures within a river can block 
fish passage, disrupt the natural flow patterns, and cause channel 
degradation and erosion (see ``Geomorphology Changes'' section above) 
that directly impact aquatic life habitat, as well as reduce the 
capacity of the stream to carry water (TNC 2004, p. 17). Streams with 
highly altered flow regimes often become wide, shallow, and 
homogeneous, resulting in poor habitat for many fish species (Bunn and 
Arthington 2002, pp. 493-498). The decline of the pearl darter in the 
Pearl River was noted after the construction of low sill dams. Bart (in 
TNC 2004, p. 5) speculated that, after spawning, young darters in the 
Pearl River were swept downriver and unable to migrate back upriver due 
to the low water sills and varied water flow; their limited success 
year after year likely caused the population to crash. These low sill 
dams are also thought to have led to the extirpation of the Alabama 
shad (Alosa alabamae) from that system (Mickel et al. 2010, p. 158).
    The proposed damming of Little and Big Cedar Creeks, tributaries to 
the Pascagoula River, for establishment of two recreational lakes 
(George County Lakes) (U.S. Army Corps of Engineers 2015, pp. 1-13) has 
prompted the American Rivers organization to recently list the 
Pascagoula River as the 10th most endangered river in the country 
(American Rivers 2016, pp. 20-21). Though the proposed project is not 
directly within known pearl darter habitat, the lakes may decrease 
water quantity entering the lower Pascagoula basin and will likely 
concentrate pollutants, reduce water flow, and alter downstream food 
webs and aquatic productivity (Poff and Hart 2002, p. 660).
Summary of Factor A
    Habitat modification and resultant water quality degradation are 
occurring within the pearl darter's current range and likely led to the 
loss of the species from the Pearl River drainage. Water quality 
degradation occurs locally from point and nonpoint source pollution in 
association with land surface, stormwater, and effluent runoff from 
urbanization, industry, and municipal areas. Of particular concern is 
the threat of overflooding of storage ponds for industrial effluent, 
such as that from pulp and paper manufacturing. Increased sediment from 
a variety of sources, including geomorphological changes and bank 
instability from past habitat modification, appears to be the major 
contributor to water quality declines in this species' habitat. 
Localized sewage and waste water effluent also pose a threat to this 
species and its habitat. The pearl darter's vulnerability to 
catastrophic events, particularly the release of pollutants in its 
habitat from oil spills, train derailments, and hydraulic fracturing, 
is also a concern due to the abundance of oil wells, pumping stations, 
gas lines, and railways throughout its habitat, and the increased 
interest in alternative oil and gas collection methods in the area. The 
proposed damming of Big and Little Cypress Creeks may decrease water 
flow and increase nutrient concentration into the Pascagoula River. 
These threats continue to impact water quality and habitat conditions 
through much of this species' current range. Therefore, we conclude 
that habitat degradation is presently a moderate threat to the pearl 
darter that is expected to continue and possibly increase into the 
future.

Factor B: Overutilization for Commercial, Recreational, Scientific, or 
Educational Purposes

    The pearl darter is not a commercially valuable species, and 
collecting is not considered a factor in its decline. Therefore, we do 
not consider overutilization for commercial, recreational, scientific, 
or educational purposes to be a threat to the pearl darter at this 
time.

Factor C: Disease or Predation

    We have no specific information indicating that disease or 
predation is negatively impacting pearl darter populations. Therefore, 
we do not consider these factors to be threats to the pearl darter at 
this time.

Factor D: The Inadequacy of Existing Regulatory Mechanisms

    The State of Mississippi classifies the pearl darter as endangered 
(Mississippi Natural Heritage Program 2015, p. 2), and prohibits the 
collection of the pearl darter for scientific purposes without a State-
issued collecting permit. However, as discussed under Factor B, we have 
no evidence to suggest that scientific collection poses a threat to 
this species. This State classification conveys no legal protection for 
the pearl darter's habitat nor does it prohibit habitat degradation, 
which is the primary threat to the species. The pearl darter receives 
no protection in Louisiana, where it is considered to have historically 
occurred (Louisiana Department of Wildlife and Fisheries 2005, p. 39).
    The pearl darter and its habitats are afforded some protection from 
water quality and habitat degradation under the Clean Water Act of 1972 
(33 U.S.C. 1251 et seq.) and the Mississippi Water Pollution Control 
Law, as amended, 1993 (Code of Mississippi, section 49-17-1, et seq.) 
and regulations promulgated thereunder by the Mississippi Commission on 
Environmental Quality. Although these laws have resulted in some 
enhancement in water quality and habitat for aquatic life, particularly 
in reducing point-source pollutants, they have been inadequate in fully 
protecting the pearl darter from sedimentation and other nonpoint 
source pollutants.
    The State of Mississippi maintains water-use classifications 
through issuance of National Pollutant Discharge Elimination System 
permits to industries, municipalities, and others that set maximum 
limits on certain pollutants or pollutant parameters. For water bodies 
on the Clean Water Act section 303(d) list of impaired streams, the 
State is required to establish a TMDL for the pollutants of concern 
that will improve water quality to the applicable standard. The 
establishment of TMDLs for 89 river or stream segments and ratings of 
fair to poor for 39 percent of the tributaries within the Pascagoula 
basin are indicative of water pollution impacts within the pearl 
darter's habitat (MDEQ 2008a, p. 17). TMDLs are not an enforced 
regulation, and only reflect benchmarks for improving water quality; 
they have not been successful in reducing water quality degradation 
within this species' habitat, as these streams continue to remain on 
the 303(d) list of impaired streams.
    Mississippi Surface Mining and Reclamation Law, Miss. Code Ann. 
section 53-7-1 et seq., and Federal laws regarding oil and gas drilling 
(42 U.S.C. 6921) are generally designed to protect freshwater resources 
like the pearl darter, but these regulatory mechanisms do not contain 
specific provisions requiring an analysis of project impacts to fish 
and wildlife resources. They also do not contain or provide for any 
formal mechanism requiring coordination with, or input from, the 
Service or the

[[Page 43892]]

Mississippi Department of Wildlife, Fisheries and Parks regarding the 
presence of federally endangered, threatened, or candidate species, or 
other rare and sensitive species. In the case of surface mining, 
penalties may be assessed if damage is serious, but there is no 
immediate response for remediation of habitats or species. As 
demonstrated under Factor A, periodic declines in water quality and 
degradation of habitat for this species are ongoing despite these 
protective regulations. These mechanisms have been inadequate to 
protect the species from sediment runoff and turbidity within its 
habitat associated with land surface runoff and municipal and 
industrial discharges, as described under Factor A. There are currently 
no requirements within the scope of other statewide environmental laws 
to specifically consider the pearl darter or ensure that a project will 
not significantly impact the species.
    The pearl darter likely receives ancillary protection (i.e., water 
quality improvements, protection from geomorphological changes) where 
it co-occurs with two other federally listed species, the Gulf sturgeon 
(Acipenser oxyrhynchus desotoi) and yellow-blotched map turtle 
(Graptemys flavimaculata), during the course of consultation on these 
species under section 7 of the Act. However, protective measures 
through section 7 of the Act would be triggered only for those projects 
having a Federal nexus, which would not include many of the water 
quality disturbances caused by industry, municipalities, agriculture, 
or private landowners.
    Additional protection of 53,520 hectares (ha) (132,128 acres (ac)) 
within the Pascagoula basin watershed occurs due to the Mississippi 
Wildlife, Fisheries and Parks' management of six Wildlife Management 
Areas (WMAs) within the upper drainage basin for recreational hunting 
and fishing. Four of the six WMAs (Chickasawhay and Leaf Rivers, Mason 
and Red Creeks) do not directly border the river system, but they do 
contain and protect parcels of upland buffer, wetland, and tributaries 
to the basin. The Pascagoula River and Ward Bayou WMAs (20,329 ha; 
50,234 ac) consist of wetland buffer and river/stream reach protecting 
approximately 106 km (66 mi) of the Pascagoula River main stem (Stowe 
in litt. 2015). The Nature Conservancy (TNC) protects 14,164 ha (35,000 
ac) within the Pascagoula River watershed and approximately 10 km (6 
mi) of the Pascagoula River shoreline in Jackson County, Mississippi. 
Of that amount, the Charles M. Deaton Nature Preserve (1,336 ha, 3,300 
ac) protects the upper reaches of the Pascagoula River, where the Leaf 
and Chickasawhay Rivers converge, and is part of a 19,020-ha (47,000-
ac) swath of public lands surrounding the Pascagoula River, which 
includes approximately 8 km (5 mi) of the Chickasawhay River and 
approximately 7 km (4 mi) of the Leaf River shorelines (Stowe in litt. 
2015).
    These State-managed WMAs and TNC preserves provide a measure of 
protection for approximately 134 km (84 mi) or 30 percent of the river 
reaches within this species' current range. Point and nonpoint sediment 
sources are decreased or reduced by using and monitoring certified BMPs 
during silviculture, road maintenance, and other landscape-altering 
activities. However, only short segments of shoreline in the 
Chickasawhay and Leaf Rivers are within these WMAs. Remaining lands 
within these segments can be vulnerable to farming and timbering to the 
bankside edge, and construction of structures such as houses, septic 
facilities, dams, and ponds. Each land management action can increase 
stormwater runoff laden with sediment and agricultural and wastewater 
chemicals. The impact of silvicultural activities on water quality 
degradation are likely lower than other land-altering activities 
according to information in the Mississippi Forestry Commission's 
report (2016, entire) that found certified BMP implementation rates to 
be high across all silvicultural landscapes in Mississippi.

Summary of Factor D

    Despite existing authorities such as the Clean Water Act, 
pollutants continue to impair the water quality throughout much of the 
current range of the pearl darter. State and Federal regulatory 
mechanisms have helped reduce the negative effects of point source and 
nonpoint source discharges, yet these regulations are difficult to 
implement, and may not provide adequate protection for sensitive 
species like the pearl darter. Thus, we conclude that existing 
regulatory mechanisms do not adequately protect the pearl darter from 
the impact of other threats.

Factor E: Other Natural or Manmade Factors Affecting Its Continued 
Existence

Small Population Size and Loss of Genetic Diversity
    The pearl darter has always been considered rare (Deacon et al. 
1979, p. 42) and is currently restricted to localized sites within the 
Pascagoula River drainage. Genetic diversity has likely declined due to 
fragmentation and separation of reproducing pearl darter populations. 
Kreiser et al. (2012, pp. 12-17) found that disjunct populations of 
pearl darters within the Leaf and Chickasawhay Rivers showed some 
distinct alleles suggesting that gene flow between the two rivers was 
restricted and perhaps that the total gene pool diversity was 
declining. Collecting data (Ross 2001, p. 500; Bart and Piller 1997, p. 
4; Bart and Suttkus 1996, p. 4; Suttkus et al. 1994, p. 19) indicate 
that the pearl darter is rare in the Pascagoula River system, as when 
this species is collected it is typically in low numbers and a 
disproportionately low percentage of the total fish collected (catch 
per unit effort of 2.1 individuals per site, Clark and Shaefer 2015, p. 
4).
    Species that are restricted in range and population size are more 
likely to suffer loss of genetic diversity due to genetic drift, 
potentially increasing their susceptibility to inbreeding depression, 
decreasing their ability to adapt to environmental changes, and 
reducing the fitness of individuals (Allendorf and Luikart 2007, pp. 
117-146; Soul[eacute] 1980, pp. 157-158). It is likely that some of the 
pearl darter populations are below the effective population size 
required to maintain long-term genetic and population viability 
(Soul[eacute] 1980, pp. 162-164).
    The long-term viability of a species is founded on the conservation 
of numerous local populations throughout its geographic range (Harris 
1984, pp. 93-104). The presence of viable, separate populations is 
essential for a species to recover and adapt to environmental change 
(Noss and Cooperrider 1994, pp. 264-297; Harris 1984, pp. 93-104). 
Inbreeding and loss of neutral genetic variation associated with small 
population size reduces the fitness of the population (Reed and 
Frankham 2003, pp. 230-237) and accelerates population decline (Fagan 
and Holmes 2006, pp. 51-60). The species' small numbers within 
scattered locations, coupled with its lack of genetic variability, may 
decrease the species' ability to adapt or recover from major 
hydrological events that impact potential spawning habitat (Clark and 
Schaefer 2015, pp. 18-22).
Hurricanes
    Fish and aquatic communities and habitat, including that of the 
pearl darter, may be changed by hurricanes (Schaefer et al. 2006, pp. 
62-68). In 2005, Hurricane Katrina destroyed much of the urban and 
industrial areas along the lower Pascagoula River basin and also 
impacted the ecology upriver to the confluence with the Leaf and

[[Page 43893]]

Chickasawhay Rivers. Many toxic chemicals that leaked from grounded and 
displaced boats and ships, storage facilities, vehicles, septic 
systems, business sites, and other sources due to the hurricane were 
reported in the rivers, along with saltwater intrusion from the Gulf of 
Mexico. Initial assessment identified several fish kills and increased 
surge of organic material into the waters, which lowered dissolved 
oxygen levels (Schaefer et al. 2006, pp. 62-68). As discussed below, 
the deleterious impacts of climate change will likely lead to an 
increase in the strength and frequency of hurricanes.
Climate Change
    Numerous long-term climate changes have been observed including 
widespread changes in precipitation amounts, ocean salinity, wind 
patterns, and aspects of extreme weather including droughts, heavy 
precipitation, heat waves, and the intensity of tropical cyclones 
(Intergovernmental Panel on Climate Change 2014, p. 4). Climate change, 
and the resultant shifts in spatial distribution, may result in 
increased fragmentation which would increase the vulnerability of any 
isolated populations to future extinction (Comet et al. 2013, p. 635). 
However, while continued change is certain, the magnitude and rate of 
change is unknown in many cases.
    Climate change has the potential to increase the vulnerability of 
the pearl darter to random catastrophic events (Thomas et al. 2004, pp. 
145-148; McLaughlin et al. 2002, pp. 6060-6074). An increase in both 
severity and variation in climate patterns is expected, with extreme 
floods, strong storms, and droughts becoming more common 
(Intergovernmental Panel on Climate Change 2014, pp. 58-83). Thomas et 
al. (2004, pp. 145-148) report that frequency, duration, and intensity 
of droughts are likely to increase in the Southeast as a result of 
global climate change. Kaushal et al. (2010, p. 465) reported that 
stream temperatures in the Southeast have increased roughly 0.2-0.4 
[deg]C (0.3-0.7[emsp14][deg]F) per decade over the past 30 years, and 
as air temperature is a strong predictor of water temperature, stream 
temperatures are expected to continue to rise. Predicted impacts of 
climate change on fishes, related to drought, include disruption to 
their physiology (e.g., temperature tolerance, dissolved oxygen needs, 
and metabolic rates), life history (e.g., timing of reproduction, 
growth rate), and distribution (e.g., range shifts, migration of new 
predators) (Comte et al. 2013, pp. 627-636; Strayer and Dudgeon 2010, 
pp. 350-351; Heino et al. 2009, pp. 41-51; Jackson and Mandrak 2002, 
pp. 89-98). However, estimates of the effects of climate change using 
available climate models typically lack the geographic precision needed 
to predict the magnitude of effects at a scale small enough to 
discretely apply to the range of a given species. Therefore, there is 
uncertainty about the specific effects of climate change (and their 
magnitude) on the pearl darter. However, climate change is almost 
certain to affect aquatic habitats in the Pascagoula River basin 
through increased water temperatures resulting in stronger storm surges 
and more frequent droughts (Alder and Hostetler 2013, pp. 1-12), and 
species with limited ranges, fragmented distributions, and small 
population sizes are thought to be especially vulnerable to the effects 
of climate change (Byers and Norris 2011, p. 18).
Summary of Factor E
    The pearl darter's limited geographic range, fragmented 
distribution within the Pascagoula River system, small population 
numbers, and low genetic diversity threaten this species' long-term 
viability. These threats are current and are likely to continue or 
increase in the future, and would be exacerbated by climate change.

Cumulative Effects of Factors A Through E

    The threats that affect the pearl darter are important on a threat-
by-threat basis but are even more significant in combination. Due to 
the loss of the species from the Pearl River system, the pearl darter 
is now confined to a single drainage system. The species continues to 
be subjected to water quality degradation from point and nonpoint 
source pollution in association with land-altering activities, 
discharges from municipalities, and geomorphological changes from past 
gravel mining. The laws and regulations directed at preventing water 
quality degradation have been ineffective at providing for the 
conservation of the pearl darter. Furthermore, these threats and their 
effect on this species are exacerbated due to the pearl darter's small 
population numbers, localized distribution, and low genetic diversity, 
which reduce its genetic fitness and resilience to possible 
catastrophic events. Though projecting possible synergistic effects of 
climate change on the pearl darter is somewhat speculative, climate 
change, and its effects of increased water temperatures leading to 
stronger storms and more frequent droughts, will have a greater 
negative impact on species with limited ranges and small population 
sizes, such as the pearl darter. While these threats or stressors may 
act in isolation, it is more probable that many stressors are acting 
simultaneously (or in combination) on the pearl darter, having a 
greater cumulative negative effect than any individual stressor or 
threat.

Determination

    We have carefully assessed the best scientific and commercial 
information available regarding the past, present, and future threats 
to the pearl darter. The pearl darter has been extirpated from the 
Pearl River system, and it is now confined to the Pascagoula River 
watershed. The species occurs in low numbers within its current range, 
and continues to be at risk throughout all of its range due to the 
immediacy, severity, and scope of threats from habitat degradation and 
range curtailment (Factor A) and other natural or manmade factors 
affecting its continued existence (Factor E). Existing regulatory 
mechanisms have been inadequate in ameliorating these threats (Factor 
D).
    Anthropogenic activities, such as general land development, 
agriculture and silviculture, oil and gas development (especially when 
BMPs were not implemented during these activities), along with 
inadequate sewage treatment, uncontrolled stormwater runoff, pulp mill 
effluent, past gravel mining and resultant geomorphological changes, 
and construction of dams or sills, have all contributed to the 
degradation of stream habitats and water quality within this species' 
range (Factor A). These land use activities have led to chemical and 
physical changes in the main stem rivers and tributaries that continue 
to affect the species through negative impacts to its habitat. Specific 
water quality threats include inputs of sediments covering bottom 
stream substrates, increased turbidity, and inputs of dissolved solids. 
These threats, especially the inputs of dissolved solids, chemical-
laden effluent, sedimentation, and geomorphic changes, have had 
profound negative effects on pearl darter populations, as demonstrated 
in the Pearl River basin, and have been the primary factor in the 
species' decline. Existing regulatory mechanisms (e.g., the Clean Water 
Act) have provided for some improvements in water quality and habitat 
conditions across the species' range, but these laws and regulations 
have been inadequate in protecting the species' habitat (Factor D), as 
evidenced by the extirpation of the species within the Pearl River 
basin and by the number of section 303(d) listed streams within the 
species'

[[Page 43894]]

historical and current range. The pearl darter's vulnerability to these 
threats is even greater due to its reduced range, scattered locations 
of small populations, and low genetic diversity (Factor E).
    The Act defines an endangered species as any species that is ``in 
danger of extinction throughout all or a significant portion of its 
range'' and a threatened species as any species ``that is likely to 
become endangered throughout all or a significant portion of its range 
within the foreseeable future.'' We find that the pearl darter is 
likely to become endangered throughout all or a significant portion of 
its range within the foreseeable future, based on the immediacy, 
severity, and scope of the threats currently impacting the species. 
Foreseeable future for this species was determined to be approximately 
20 years, which is based on our best professional judgement of the 
projected future conditions related to threats identified impacting 
this species. The overall range has been reduced substantially, and the 
remaining habitat and populations are threatened by a variety of 
factors acting in combination to reduce the overall viability of the 
species over time. The threats are not expected to change substantially 
within this 20-year timeframe, as water quality degradation continues 
to pose a risk locally despite existing regulations, and land 
development and land-altering activities are expected to increase. The 
risk of becoming endangered during this time is high because 
populations confined to this single watershed are fragmented and 
geneti