Species Status Assessment Report Bridled Darter (Percina Kusha)

Species Status Assessment Report for the Bridled Darter (Percina kusha)

Version 1.0

Photo by Noel Burkhead

July 2017

U.S. Fish and Wildlife Service

Region 4

Atlanta, GA

Executive Summary

This species status assessment (SSA) reports the results of the comprehensive status review for the bridled darter (Percina kusha), documenting the species’ historical condition and providing estimates of current and future condition under a range of different scenarios. The bridled darter is small fish native to the upper Coosa River basin in Georgia and Tennessee that occurs in small rivers with good water quality.

The SSA process can be categorized into three sequential stages. During the first stage, we consider the bridled darter’s life history and use the conservation biology principles of resiliency, redundancy, and representation (together, the 3 Rs) to better understand the “needs” of populations and the species to maintain viability. The next stage involved an assessment of the historical and current condition of the species’ demographics and habitat characteristics. The final stage of the SSA involved making predictions about future viability while considering the species’ responses to anthropogenic and environmental influences that are likely to occur within its range. This process used the best available information to characterize viability as the ability of a species to sustain populations in the wild over time.

To evaluate the current and future viability of the bridled darter, we assessed a plausible range of conditions that affect bridled darter habitats to allow us to forecast the species’ resiliency, representation, and redundancy. For the purposes of this assessment, populations were delineated using U.S. Geological Survey 10 digit Hydrologic Unit Codes (HUC10s) that are occupied by bridled darter.

Resiliency, assessed at the population level, describes the ability of a population to withstand stochastic events. A species needs multiple resilient populations distributed across its range to persist into the future and avoid extinction. A number of factors, including (but not limited to) water quality, water quantity, habitat connectivity, and instream substrate, may influence whether bridled darter populations will occupy available habitat. As we considered the future viability of the species, more populations with high resiliency distributed across the known range of the species can be associated with higher species viability. As a species, the bridled darter has limited resiliency, with the majority of populations considered to be in low resiliency.

Redundancy describes the ability of a species to withstand catastrophic events. Measured by the number of populations, their resiliency, and their distribution (and connectivity), redundancy gauges the probability that the species has a margin of safety to withstand or can bounce back from catastrophic events (such as a rare destructive natural event or episode involving many populations). Redundancy for the bridled darter is characterized by having multiple, resilient and representative populations distributed throughout its range. Furthermore, these populations should maintain natural levels of connectivity between them. Connectivity allows for immigration and emigration between populations and increases the likelihood of recolonization should a population become extirpated.

Representation describes the ability of a species to adapt to changing environmental conditions. Representation can be measured by the breadth of genetic or environmental diversity within and among populations and gauges the probability that a species is capable of adapting to environmental changes. The more representation, or diversity, a species has, the more it is capable of adapting to changes (natural or human caused) in its environment. In the absence of species-specific genetic and ecological diversity information, we evaluate representation based on the extent and variability of habitat characteristics across the geographical range.

The analysis of species’ current condition revealed that the extent of occupied habitat has declined, with most populations (5 of 6) occupying 33-66% of the historically occupied ranges. All historically known populations remain extant; however, there is little connectivity between them and abundances are qualitatively low.

To assess the future condition of the bridled darter, a variety of stressors from urbanization, agriculture, and climate were considered. Populations with low resiliency are considered to be more vulnerable to extirpation, which, in turn would decrease species’ level representation and redundancy. To help address uncertainty associated with the degree and extent of potential future stressors, the 3Rs were assessed using three plausible future scenarios. These scenarios were based, in part, on the results of urbanization and climate models.

An important assumption of the predictive analysis was that future population resiliency is largely dependent on water quality, water flow, and structural habitat conditions. Our assessment predicted that all currently extant bridled darter populations would experience negative changes to these important habitat requisites in the future.

Given scenario 1, the “Status Quo” option, loss of resiliency, representation, and redundancy is expected. Under this secenario, we predicted that two populations would likely be extirpated and the remaining populations would have low resiliency. The extirpation of two populations would reduce redundancy by 33%. Representation would be reduced due to the loss of the only known population in the Coosawattee River basin and range contraction out of Piedmont and Ridge and Valley physiographic provinces.

Given scenario 2, the “Best Case” option, we predicted slight improvements to resiliency from the current conditions. No populations would exhibit “high” resiliency, three would be considered “moderate” resiliency and two would be “low” resiliency. Redundancy and representation would be consistent with current conditions.

Given scenario 3, the “Worst Case” option, loss of resiliency, representation, and redundancy is expected. Under this scenario, we predicted that three populations would likely be extirpated and the remaining populations would have low resiliency. Redundancy would be reduced by 50% in the Conasauga River basin and 33% in the Etowah River basin. The extirpation of three populations would reduce overall redundancy by 50%. Representation would be reduced due to

3 the loss of the only known population in the Coosawattee River basin and range contraction out of Piedmont and Ridge and Valley physiographic provinces.

Table E1. Current estimated resiliency and predicted future resiliency of populations under multiple scenarios

Population Current Status Quo Best Case Worst Case Conasauga River Low Low Moderate Low Holly Creek Low Low Low Likely Extirpated Talking Rock Low Likely Extirpated Low Likely Extirpated Creek Long Swamp Low Likely Extirpated Low Likely Extirpated Creek Amicalola Creek Low Low Moderate Low Etowah River Low Low Moderate Low

Overall Summary

Currently, the bridled darter continues to occupy all streams where it was known to occur historically. Based on collection records from the last 10 years, five populations occur over shorter overall stream lengths than historical records, indicating range reduction in these five populations. No population of bridled darter currently exhibits high resiliency due to the reduction in extent of occupied habitat, low abundance of individuals per collection record, a linear simple, arrangement of records, as well as stressors affecting habitat and water quality. Similarly, representation and redundancy is currently low for this species because multiple resilient populations are lacking, connectivity is limited among populations, and this species is increasingly becoming isolated to the upstream limits of its range in the Blue Ridge physiographic province.

Our future scenarios assessment considered the current viability of the species to project likely future viability given plausible scenarios of urban development and climate change. Only in the Best Case scenario did the species persist in all known populations. However, under this scenario bridled darters were not expected to expand outside of historical range boundaries and resiliency was expected to be moderate at best. Two and three populations were extirpated under the Status Quo and Worst Case scenarios, respectively. Resiliency, representation, and redundancy declined in both these scenarios due to further range contractions and increased likelihoods for extreme climatic events to impact populations.

Table of Contents

EXECUTIVE SUMMARY……………………………………………………………………….2 CHAPTER 1 – INTRODUCTION………………………………………………………………..6 CHAPTER 2 – SPECIES BIOLOGY AND INDIVIDIUAL NEEDS……………………………8 Taxonomic History and Uncertainty………………………………………………………8 Physical Description…………………………………………………………...………….9 Range and Distribution……………………………………………………………………9 Biology, Life history, Ecology……………………………………………………………12 CHAPTER 3 – POPULATION AND SPECIES NEEDS……………………………………….15 Bridled Darter Resiliency………………………………………………………………..15 Bridled Darter Representation…………………………………………………………..17

Bridled Darter Redundancy……………………………………………………………...18 CHAPTER 4 – FACTORS INFLUENCING VIABILITY……………………………………...19 Urbanization……………………………………………………………………………..19

Agriculture……………………………………………………………………………….22 Sedimentation…………………………………………………………………………….24

Loss of Riparian Vegetation……………………………………………………………...25

Weather events…………………………………………………………………………...26

Conservation Measures………………………………………………………………….27

CHPATER 5 – CURRENT WATERSHED AND POPULATION……………………………..29 Methods…………………………………………………………………………………..29 Current Condition………………………………………………………………………..34

CHAPTER 6 – FUTURE VIABILITY…………………………………………………………..50

Methods…………………………………………………………………………………..50

Status Quo………………………………………………………………………………..52

Best Case…………………………………………………………………………………62

Worst Case……………………………………………………………………………….68

Summary…………………………………………………………………………………73

LITERATURE CITED…………………………………………………………………………..78

Chapter 1. Introduction

The bridled darter is a freshwater fish found in the Coosa River System in the Blue Ridge, Ridge and Valley, and Piedmont physiographic provinces. This species was petitioned for federal listing under the Endangered Species Act of 1973, as amended (Act), as part of the 2010 Petition to List 404 Aquatic, Riparian and Wetland Species from the Southeastern United States by the Center for Biological Diversity (CBD 2010, p. 824).

The Species Status Assessment (SSA) framework (USFWS 2016, entire) is intended to be an in- depth review of the species’ biology and threats, an evaluation of its biological status, and an assessment of the resources and conditions needed to maintain long-term viability. The intent is for the SSA Report to be easily updated as new information becomes available and to support all functions of the Endangered Species Program from Candidate Assessment to Listing to Consultations to Recovery. As such, the SSA Report will be a living document upon which other documents, such as listing rules, recovery plans, and 5-year reviews, would be based if the species warrants listing under the Act.

The SSA Report is not a decisional document by the U.S. Fish and Wildlife Service (Service), rather it provides a review of available information strictly related to the biological status of the bridled darter. The listing decision will be made by the Service after reviewing this document and all relevant laws, regulations, and policies, and the results of a proposed decisions will be announced in the Federal Register, with appropriate opportunities for public input.

For the purpose of this assessment, we generally define viability as the ability of the bridled darter to sustain populations in natural river systems over time. Using the SSA framework (Figure 1.1), we consider what the species needs to maintain viability by characterizing the status of the species in terms of its resiliency, redundancy, and representation (Wolf et al. 2015, entire).

Figure 1. Species StatusAssessment Framework

• Resiliency describes the ability of populations to withstand stochastic events (arising from random factors). We can measure resiliency based on metrics of population health; for example, species abundance and complexity of their spatial occurrences. Highly resilient populations are better able to withstand disturbances such as random fluctuations in birth rates (demographic stochasticity), variations in rainfall (environmental stochasticity), or the effects of anthropogenic activities.

• Representation describes the ability of a species to adapt to changing environmental conditions. Representation can be measured by the breadth of genetic or environmental diversity within and among populations and gauges the probability that a species is capable of adapting to environmental changes. The more representation, or diversity, a species has, the more it is capable of adapting to changes (natural or human caused) in its environment. In the absence of species-specific genetic and ecological diversity information, we evaluate representation based on the extent and variability of habitat characteristics across the geographical range.

• Redundancy describes the ability of a species to withstand catastrophic events. Measured by the number of populations, their resiliency, and their distribution (and connectivity), redundancy gauges the probability that the species has a margin of safety to withstand or can bounce back from catastrophic events (such as a rare destructive natural event or episode involving many populations).

To evaluate the biological status of the bridled darter both currently and into the future, we assessed a range of conditions to allow us to consider the species’ resiliency, redundancy, and representation (together, the 3Rs). This SSA Report provides a thorough assessment of biology and natural history and assesses demographic risks, stressors, and limiting factors in the context of determining the viability and risks of extinction for the species. This document is a compilation of the best available scientific and commercial information and a description of past, present, and likely future risk factors to the bridled darter.

Chapter 2: Species Biology and Individual Needs

Taxonomic History and Uncertainty

The Bridled Dater (Percina kusha) was formally described in 2007 by James Williams and Noel Burkhead and placed in the subgenus Alvordius (Williams et al. 2007, p. 9). The type locality was designated as Conasauaga River at the mouth of Minnewauga Creek, Polk County, Tennessee. At the time of description the species distribution was defined as restricted to the headwaters of the Coosa River in Georgia and Tennessee including the upper Conasauaga River and tributaries and the upper Etowah River and its tributaries.

Geographic variation within the species is known between the Etowah and Conasauga rivers. Variations in scale counts were found between individuals from the Conasauga River and the Etowah River; however, differentiation in mitochondrial DNA did not warrant classifying the Etowah population as a separate species (Williams et al. 2007, p. 9). In 2011, the subgenus Chalinoperca was introduced to which the bridled darter and muscadine darter (Percina

smithvanizi) were added (Near et al. 2011, p. 592). Within that study, it was noted that the population of bridled darter within the Etowah River system may represent a new species based on genetic information (Near et al. 2011, p. 592). Additionally, differences in spawning behavior has been documented between the Etowah and Conasauga populations. In this assessment, we acknowledge the variation between populations as important to overall representation but assess all populations of the bridled darter as a single species since there is no formal description that elevates the bridled darter in the Etowah River basin to species status.

Physical Description

Photo by Noel Burkhead

Figure 2. Bridled Darter

Adult bridled darters reach a maximum total length of 3 inches (75 mm). Like other member of the Percina genus, the Bridled Darter lacks bright colors. Males and females are similar in color, however females lack a dusky ground color found in males. The back is a pale brown to yellowish. There are 8-11 elongate oval blotches which connect to form a dark lateral stripe with undulating margins. This lateral stripe is continuous with pigmentation in front and behind the eye, giving the appearance of a horse’s bridle (leading to its common name). The breast and lower side of the head are white to cream in color and may be dusky in breeding males. [Williams et al. 2007, p. 6 and Etnier and Starnes 1993 p. 591]

Range and Distribution

At the time of its description, the bridled darter’s range was considered within the headwaters of the Coosa River basin. The bridled darter’s distribution, includes the main channel of the Conasauga River in Murray and Whitfield counties, GA, and Bradley and Polk counties, TN as well as in the Etowah River in Dawson and Lumpkin counties, GA (Williams et al. 2007, p. 9). It was also known to occur in short reaches of several tributaries to the Conasauga River including:

Holly Creek, Murray County, GA; and Bally Play and Minnewauga creeks in Polk County, TN and tributaries to the Etowah River including: Amicalola, Little Amicalola, Cochran, and Shoal creeks in Dawson County, GA (Williams et al. 2007, p. 9). The bridled darter is also known to occur in Talking Rock and Long Swamp creeks in Pickens County, GA from records predating the description.

Currently, the bridled darter continues to be found in all historically known occupied rivers, although the extent of occupied river reaches has been reduced (see Current Conditions section for a detailed overview of the current range and population resiliency).

Figure 3. Watersheds (HUC10s) in which at least one collection of bridled darter has been made.

Biology, Life history, Ecology

Habitat:

The Bridled Darter inhabits small rivers and lower reaches of tributary creeks that have been described as having “good” to “exceptional” water quality (Williams et al. 2007 pg. 10 and Etnier and Starnes pg. 592). Occupied habitat is characterized by moderate gradient with a substrate of sand, gravel, cobble, and bedrock. Bridled darters are typically found in flowing pools and backwaters adjacent to runs. This species is often found near structure like submerged logs, leaf packs, cobble, and water willow (Justicia americana) where it tends to hover above the substrate.

Feeding:

The bridled darter is a sight feeder and has been observed to pluck food from submerged objects. This species has also been observed drift-feeding. It positions itself downstream of rocks, away from fast currents, and feeds on invertebrates that are washed downstream and thrusted upward by turbulence. Feeding peaks in late afternoon before dusk. Stomach contents for individuals from the Conasauga River contained small mayfly nymphs and blackfly larvae.

Reproduction and life history:

Reproductive behavior (aggression and courtship) has been observed in the Etowah River system from March 27 – June 26 in water temperatures that ranged from 12.9-20.7 C (Anderson 2009, p. 43). Based on six spawning events observed in the Etowah River basin, the Bridled Darter spawning season likely lasts from mid-April through early June (Anderson 2009, p. 50-51). In the Conasauga River, reproductive behavior was observed from mid-May to mid-July at water temperatures from 16 – 22 C (Johnston et al. 2002, p. 2).

Spawning microhabitat in the Etowah River basin was observed upstream and downstream of swift to moderate riffles in sand and gravel at depths between 24.4 to 57.9 cm and velocities, at 60% depth, from -0.03-0.49 m/s, and velocities, at substrate, from 0.13 to 0.21 m/s (Anderson 2009, p. 42). These measurements are similar to those observed at spawning microhabitats in the Conasauga River although observed velocities were slower in the Conasauga (Johnston et al. 2002. p. 4). Spawning habitat only differed from non-spawning habitat in the Conasauga River by having slightly more sand substrates (Johnston et al. 2002, p. 2).

Spawning begins with a female being followed by a male, leading the site selection process. During site selection, competitive behavior between males for the female has been observed, with the larger males attempting to chase away smaller males. In the Conasauga River, sneaker males (smaller males that join with a spawning pair and release sperm) have been observed with some frequency (Johnston et al. 2002, p. 2).

In the Etowah River populations, upon selecting a site, the male mounts the female and the female buries her posterior abdomen into the substrate and both individuals quiver. Females have been observed to remain in the substrate for 5-10 seconds post spawning (Anderson 2009, p. 41). The same pair may undertake multiple spawning events at different locations after the initial spawn. Variation exists in the Conasauga River, where males position beside the female instead of on top (Johnston et al. 2002, p. 2). However, eggs and sperm are released and buried in a similar manner as described above. Fecundity was estimated to be low for this species with only about 75 mature ova observed per female (Etnier and Starnes, p. 592). While no information is available regarding egg incubation times for bridled darter, if we assume its life-history traits are similar to another egg-burying Percina species, blackside darter (Percina (Alvordius) maculata), than we would expect an incubation time of approximately six days (Petravicz 1938, p. 43). Similarly, we can infer that, like the blackside darter, larvae of the bridled darter are pelagic and inhabit the water column for approximately three weeks (Petravicz 1938, p. 43). Three size classes of bridled darter have been observed in the Conasauga River (50, 65, 75 mm) corresponding to three age classes and indicating a life-span of three years (Etnier and Starnes 1993, p. 592).

Table 1. Overview of needs of an individual Bridled Darter based on our knowledge of the species’ biology, ecology, and life history summarized above

Life Stage Resources Needed Information Source Fertilized Egg Clean sand or fine gravel Anderson 2009, p. 48 sediments, flowing water (DO) Larvae Clear flowing water, Petravicz 1938, p. 43 connectivity to downstream habitat to accommodate a larval drift period of three weeks

Juveniles Clear flowing water, adequate Williams et al. 2007 p. 10-11 food availability, clean Etnier and Starnes 1993 p. 592 sediments, presence of Johnston et al. 2002 p. 2-4 instream structures (woody Anderson 2009 p. 42, 48 debris, leaf packs, large rocks), low gradient stream reaches with flowing pools and backwaters immediately adjacent to runs, appropriate food availability

Adult Clear flowing water, adequate Williams et al. 2007 p. 10-11 food availability, clean Etnier and Starnes 1993 p. 592 sediments, presence of Johnston et al. 2002 p. 2 instream structures (woody Anderson 2009 p. 42, 48 debris, leaf packs, large rocks), low gradient stream reaches with flowing pools and backwaters immediately adjacent to runs, appropriate food availability

Chapter 3: Population and Species Needs

Bridled Darter Resiliency

Each population of the bridled darter needs to be able to withstand or be resilient to stochastic events or disturbances. These are events that are reasonably likely to occur and can drastically alter the ecosystem. Examples of stochastic events that may affect bridled darters include drought, major storms and flooding.

To be resilient to stochastic events populations of bridled darter need to have an adequate number of individuals (abundance). It should cover a large enough area such that small localized events do not cause extirpation (spatial extent). Finally the area occupied by the population needs to exist in multiple tributaries (spatial complexity) so a single event (like a spill of toxic chemicals) cannot eliminate an entire population as it perpetuates downstream.

Population level characteristics (abundance, spatial extent, and spatial complexity) that influence resiliency are controlled by environmental conditions present in the upper Coosa River system. Population abundance, spatial extent and spatial complexity are results of successful spawning, recruitment (survival of young individuals to maturity and spawning), adult survival, and dispersal. Spawning, survival, and dispersal are all influenced by aspects of water quality, water quantity, structural habitat, and connectivity (as indicated by Table 1).

Water Quality

Bridled darters, like other benthic species are sensitive to poor water quality (Warren et al. 1997, p. 125). Broadly, good water quality for the bridled darter consists of high amounts of dissolved oxygen (DO), moderate pH (slightly acidic in the Blue Ridge and Piedmont physiographic provinces to slight basic in the Ridge and Valley physiographic province), unaltered temperature regimes, and little to no pollutants present. Degraded water quality has the potential to induce stress on individuals, reduce spawning success, or cause direct mortality.

Water Quantity (Flow Regime)

In addition to water quality, bridled darters have adapted to the perennial flows and seasonal predictability of their preferred habitat in small rivers (water quantity). Low flows can negatively affect water quality parameters (temperature and DO), prevent fine sediments, contaminants, and excess nutrients from being flushed downstream, and lead to temporary eutrophication (thereby reducing DO). Low flows can also concentrate bridled darters into pools exposing them to predation or stress resulting from high density of organisms concentrated in wetted pools. Conversely, extremely high flows can also negatively affect populations of bridled darters. Extensive scour and loss of habitat along river margins after extreme storms and flooding can cause localized declines in abundance of fish species (USFWS 2011, p. 9). Finally, altered flow regimes seen downstream of dams and around urban areas can negatively alter structural habitat

through scouring, decouple timing of life history patterns from requisite flows, and alter temperature regimes, DO concentrations, and sedimentation (Bunn and Arthington 2002, entire).

Structural Habitat

Structural habitat provides the necessary physical features for bridled darters to spawn, forage, and seek refuge from predators or high flows. Structural habitat refers to substrate (gravel, cobble, and sand), boulders, large woody debris, and leaf packs utilized by bridled darters (see Table 1). Clean substrates (free of fine sediment) ensure adequate DO levels are available for developing eggs. Additionally, a lack of fine sediments maintains adequate interstitial spaces (voids underneath and between rocks and logs) for the bridled darter to feed and shelter. The small rivers where the bridled darter is found receive woody material from riparian areas that provide additional structural habitat that is used by bridled darter for foraging. Woody material and other terrestrial plant material, such as leaves, that enters streams and rivers are the primary source of nutrients and form the base of the food web for the river ecosystem where the bridled darter occurs. Therefore, terrestrial plant material provides structure for shelter and foraging and directly influences food resources on which the bridled darter depends (Vannote et al. 1980, p. 132).

Connectivity

Connectivity, for the purpose of this assessment, refers to a species’ ability to disperse to and from habitat patches (Gido et al. 2010, p 293) and is dependent on natural or artificial features present on a river or stream (e.g. waterfalls or dams). We consider that longitudinal connectivity (movement parallel with the river in an upstream or downstream direction) to be the most relevant for the bridled darter. The bridled darter has adapted to an ecosystem that would naturally provide connectivity (with the exception of isolation in the Etowah River system as indicated by morphological and behavioral variations). Therefore, the bridled darter has adapted to an ecosystem that would allow it to repopulate areas where localized extirpation during natural stochastic events may have occurred. Additionally, natural connectivity would allow the bridled darter to maintain gene flow across the multiple occupied rivers. Therefore, factors that reduce connectivity (dams or culverts that act as barriers) would limit dispersal, reduce the species’ ability to recolonize after disturbance events, limit gene flow, increase genetic drift, reduce genetic variability (within populations), increase genetic variability among populations, and culminate in increased risk of extirpation and extinction (Gido et al 2010, p. 296; Gaggiotti 2003, p. 160).

Figure 4. Influence diagram illustrating how habitat factors influence breeding, feeding, and sheltering factors, which in in turn affect demographic factors that ultimately drive fish population growth and maintenance.

Bridled Darter Representation

Representation describes the ability of a species to adapt to changing environmental conditions over time and encompasses the “ecological and evolutionary patterns and processes that not only maintain but also generate species” (Shaffer and Stein, p. 308). It is characterized by the breadth of genetic and environmental diversity within and among populations. For the bridled darter to exhibit adequate representation, resilient populations should occur in all physiographic provinces to which it is native (Blue Ridge, Ridge and Valley, Piedmont). These occupied physiographic provinces represent the ecological setting in which the bridled darter has evolved. Additionally, evolutionary patterns that are exhibited by the morphological, genetic, and behavioral variation that exists within the species should be maintained. For the bridled darter, this variation has currently been identified as behavioral and morphological differences between Etowah and Conasauga River populations. It is unknown whether variation exists in Talking Rock Creek, Holly Creek, Long Swamp Creek, or Amicalola Creek; however, maintaining representation across occupied watersheds would ensure cryptic diversity is maintained. Finally, natural levels of connectivity are important to be maintained between representative populations because it allows for the exchange of novel and beneficial adaptations where connectivity is high or is the mechanism for localized adaption and variation where connectivity is lower and the species is naturally more isolated.

Bridled Darter Redundancy

Redundancy describes the ability of a species to withstand catastrophic events. It “guards against irreplaceable loss of representation” (Redford et al. 2011 p. 42; Tear et al. 2005 p. 841) and minimizes the effect of localized extirpation on the range-wide persistence of a species (Shaffer and Stein, p. 308). Redundancy for the bridled darter is characterized by having multiple, resilient and representative populations distributed throughout its range. Furthermore, these populations should maintain natural levels of connectivity between them. Connectivity allows for immigration and emigration between populations and increases the likelihood of recolonization should a population become extirpated.

Figure 5. Resiliency, representation, and redundancy are interrelated conservation biology principles that can be used to evaluate the current and future condition of a species. Some components that influence resiliency, representation, and redundancy are provided.

Chapter 3: Factors that Influence Viability

The upper Coosa River basin has been identified as a priority region for conservation by numerous agencies and researchers (Service, Georgia Department of Natural Resources,

University of Georgia). Efforts have been made in parts of this region to implement watershed wide conservation plans (Etowah Habitat Conservation Plan, Conasauga Working Lands for Wildlife (WLFW)). Because of the high level of interest by researchers and management agencies in the area, factors that affect aquatic habitats in the upper Coosa River basin have been identified and described (Freeman et al. 2002, Wenger and Freeman 2006). The current and potential future effects of these factors, along with information about populations help to inform species viability and vulnerability to extinction.

Urbanization

Urbanization refers to a change in land cover and land use from forests or agriculture to increased density of residential and commercial infrastructure. Urbanization is expected to affect the bridled darter across its range due to the majority of known localities occurring in close vicinity to the Atlanta metropolitan area and areas with growing populations and increasing development that exist between Chattanooga and Atlanta. Urbanization introduces a multitude of stressors into lotic systems that co-vary and have synergistic effects that are difficult to disentangle (Matthaei and Lang 2016, p. 180). Streams affected by urbanization have been described to exhibit an “urban stream syndrome” (Matthaei and Lang 2016, p. 180; Wenger et al. 2009, entire; Walsh et al. 2005, p. 207). The urban stream syndrome consistently includes “a flashier hydrograph, elevated concentrations of nutrients and contaminants, altered channel morphology and stability, and reduced biotic richness, with an increased dominance of species tolerant to poor water quality and variably includes reduced baseflow and increased suspended solids” (Walsh et al. 2005, p. 207; Paul and Meyer 2001, entire). Therefore, where urbanization occurs, it is anticipated to increase the magnitude of nearly all stressors present within the bridled darter’s occupied range.

Water Quantity

A major feature of urbanized areas is an overall increase in impervious surfaces. Impervious surfaces can be defined as hard surfaces that preclude water infiltration such as paved roads, parking lots, roofs, and even highly compacted soil like sports fields. Runoff from impervious surfaces directly affects stream flows and water quantity by altering the natural hydrologic cycle of streams and rivers and introduces more flow variability (flashy flows). In a natural forested system, most rainfall soaks in to the soil and is carried into nearby streams via subsurface flow. Some evaporates or transpires, and a relatively small amount travels to streams via overland flow. Generally, in a natural, forested Southeastern watershed, there is a time-lag between a rainfall event and peak flows after a rain event, peak flows are moderated due to evaporation, transpiration, and percolation into groundwater, and baseflows are maintained by groundwater input that is consistently recharged due to percolation of rainwater (Figure 6). However, in an urbanized system with a large proportion of impervious cover, most stormwater is rapidly conveyed into streams due to a lack of infiltration and reduction of evapotranspiration and diverted quickly to streams via stormwater drain pipes or ditches. As a result, storm flows in the

19 receiving stream are higher and more frequent, although shorter in duration, and base flows are lower due to a lack of groundwater recharge in an urban stream (see Figure 6). The storm discharge of urban streams can be twice that of rural streams draining watershed of similar size (Pizzuto et al. 2000, p. 81, Rose and Peters 2000, p. 1454). The bridled darter can be directly affected by flashy flows patterns induced by urbanization. The flashy flows as a result of urbanization may cause stress, displacement, or mortality (Konrad and Booth 2005, pp. 160-161) and it can decouple life-history cues and reduce spawning success (Bunn and Arthington 2002, p. 497).

Figure 6. Black bars represent a rain event, the solid line represents stream discharge in a forested watershed, and the dotted line represented discharge in an urbanized watershed. From Walsh et al. 2004.

In addition to direct effects on bridled darters, flashy stream flows and frequent, smaller high- flow events seen in urban streams negatively affects structural habitat on which the species depends. “Reduction in channel complexity, and thus instream habitat, appears an almost universal symptom of the urban stream syndrome” (Walsh et al. 2005, p. 711). This decrease in channel complexity can be seen as channel straightening (either through engineering or hydrologic processes) and a reduction in in stream cover and natural substrates like boulders, cobble, and gravel. Another result of frequent, smaller high-flow events is the low retention time (i.e. it is removed from the system quickly) of large woody structure and other terrestrial plant material (Walsh et al. 2005, p. 711). As a result, urban streams have lower amounts of plant material and bridled darter food resources are negatively affected as well as habitat used for foraging and shelter.

Water Quality

“Increased concentrations of loads of several chemical pollutants in stream water appear universal in urban streams” (Walsh et al. 2005, p. 710). Pollutants, including metals, hydrocarbons, pesticides and other potentially harmful organic and inorganic compounds, are common in urban streams. Pesticides also are heavily used in urban and suburban areas, and many of these find their way into streams and groundwater. A comparison of agricultural and urban groundwater quality in the Mobile Basin (which includes the Coosa River basin) found a greater variety and frequency of pesticide compounds in the urban groundwater (Robinson 2003, p. 27). Chlordane and other now-banned organochlorine pesticides are still common in urban streams, including those in the Mobile Basin (Zappia 2002, p. 53). Streets and parking lots can contribute large quantities of heavy metals that are largely derived from automobiles (Van Hassel et al. 1980, p. 642; Bannerman et al. 1993, p. 46). Oil and other hydrocarbons are also common constituent in urban runoff (Fam et al. 1987, p. 1045).These pollutants tend to accumulate on impervious surfaces due to the lack of infiltration and are subsequently washed into streams during rain events. In addition to pollutants that accumulate on impervious surfaces, wastewater discharges and leaky septic systems can input excess nutrients, fecal coliforms, household chemicals, and pharmaceuticals in to urban streams. Other declines in water quality parameters are observed as stream temperatures elevating to stressful levels due to stormwater becoming superheated on impervious surfaces and lower dissolved oxygen. This overall degradation of water quality makes urban streams inhospitable to aquatic species that have adapted to habitats in cool, clear, flowing water, like the bridled darter.

Infrastructure within Rivers and Streams

As discussed earlier, increases in infrastructure is current and ongoing within the range of the bridled darter. This increase in infrastructure due to growing human populations has been generally identified as increases in housing density, commercial space, and associated impervious surface cover. However, other aspects of infrastructure can directly affect stream and river ecosystems. These are engineered structures that cross or are placed directly within streams and rivers (i.e. bridges, culverts, dams, pipelines, and telecommunication lines). Structures installed at road crossings (bridges and culverts), dams, and pipelines all have the potential to act as barriers to fish movement and reduce connectivity. Fishes can be particularly susceptible to a loss of connectivity resulting from movement and dispersal barriers because their movement is restricted to the stream network. In general, barriers to fish movement can limit drift of pelagic larvae to downstream reaches, block exchange of genetic material between populations, and increase a population’s vulnerability to local extinction and prevent recolonization after extirpation has occurred.

Structures like dams, not only reduce connectivity within a watershed. They can substantially alter hydrology downstream, especially when operated for hydroelectric power generation (Freeman et al. 2001, p. 183, Power et al. 1996, p. 893). These dams are usually operated

through hydropeaking, which only produce high flows when power generation is needed. Increases in flow frequency or intensity during hydropeaking operations can result in channel widening through bank erosion or deepening to accommodate the additional discharge unless the channel is physically constrained (Wolman 1967, p. 392; Arnold et al. 1982, p. 160; Booth 1990, p. 409). This results in increased downstream sedimentation and unstable beds, both of which degrade spawning, channel complexity, feeding, and shelter habitat for riffle-dwelling species that rely on sediment-free gravel.

Non-hydropeaking reservoirs (farm ponds, amenity lakes, and other impoundments) may also substantially alter hydrologic regimes by storing water during low flow periods, effectively dampening moderate to high flows and in some cases augmenting flows. The demand for these reservoirs will increase as human populations increase to accommodate water needs. For instance, estimated water withdrawal for the Metro Atlanta Water District (which includes a portion of the bridled darter range) was 687.0 mgd while it was permitted to use up to 882 mgd and current water use budgets anticipate permitting 1,140 mgd by 2035 (Metropolitan North Georgia Planning District 2009, p. 2 - 7). Surface water has and will continue to be the major supply of fresh water in this region due to the bedrock geology (Metropolitan North Georgia Planning District 2009, p. 2 - 7).Therefore, to provide for the increase in water demand, storage reservoirs have been proposed in the upper Coosa River basin. Depending on the location of drinking water supply reservoirs, bridled darter habitat may be disconnected or destroyed.

Infrastructure placed within occupied habitats has the potential to directly destroy physical habitat within the footprint of the structure. It can reduce connectivity which limits dispersal, reduces the species’ ability to recolonize after disturbance event, limits gene flow, increases genetic drift, reduces genetic variability (within populations), increases genetic variability among populations, and culminates in increased risk of extirpation and extinction (Gido et al 2010, p. 296; Gaggiotti 2003, p. 160). In addition to the above effects, dams can also substantially alter flows and negatively affect suitable downstream habitat and temperatures and the reservoirs formed upstream of dams converts suitable flowing water habitat into lake-like habitat. Currently, the bridled darter is exposed to these stressors from numerous road crossings, two large hydropower dams, and small run-of-river dams (addressed in more detail under current conditions).

Agriculture

Agriculture is another predominant land use within the range of bridled darter. Within the Ridge and Valley province, row crop agriculture is prevalent and poultry farming is common throughout all northern Georgia. The effects of these agricultural practices on streams and rivers and the bridled darter are explained below.

Poultry Farming

Poultry production that occurs within the range of the bridled darter is undertaken primarily in poultry houses. In addition to broilers, pullets, and layer chickens, each poultry house has an estimated ability to produce up to 100 tons of litter a year. Poultry litter is a mixture of chicken manure, feathers, spilled food, and bedding material that frequently is used to fertilize pastureland or row crops that frequently occur adjacent to rivers and streams. Surface-spreading of litter allow runoff from heavy rains to carry excess nutrients from manure into nearby streams. Litter can also contain arsenic, which is formed from a chemical routinely used as a feed additive to prevent disease and stimulate growth (Stolze et al. 2007, p. 821). Other substances often found in poultry litter included fecal coliform, salmonella, and other pathogens, pesticide residue, other heavy metals (Bolan et al. 2010, pp. 676-683). In general, the input of compounds from poultry litter into rivers and streams can diminish water quality on which the bridled darter depends and cause physiological stress.

Estrogens, a type of endocrine disruptor, from poultry litter have been identified as a major threat to the Conasauga River system (Jacobs 2015, entire). Increased levels of estrogens have been found to have numerous effects of fishes including: intersex individuals and testicular oocytes (Yonkos et al. 2010, p. 2338), decreased competitive behavior (Martinovic et al. 2007, p. 275), decreased sperm concentrations and decreased sperm mobility, and delayed spermatogenesis (Aravindakshan et al. 2004, p. 161). All of these effects lead to decreases in spawning success and potentially population collapse within short time frames (Kidd et al. 2007). In a recent study of endocrine disruptors on fishes in the Conasauga River, approximately 7.5% of male fishes surveyed were found to have testicular oocytes (Jacobs 2015, p. 39). Studies have not been conducted to clarify the effects of endocrine disruptors on bridled darters; however, instances of intersex, testicular oocytes, and decreased reproductive health attributed to higher concentrations of endocrine disruptors has been observed in blackbanded (Percina nigrofasciata), speckled (Etheostma stigmaeum), rainbow (Etheostma caeruleum), and greenside (Etheostma blenniodes) darters (Jacobs et al 2015, p. 65; Tetreault et al. 2011, p. 287; Fuzzen et al. 2015, p. 111). High levels of estrogens are expected in other drainages that have similarly high numbers of poultry houses such as the Coosawattee River basin and the Amicalola River basin. Therefore, it is reasonable to infer that other rivers, besides the Conasauga River, within the Coosa basin are affected by estrogens from poultry litter and the bridled darter is exposed to their negative effects in multiple portions of its range.

Other Contaminants

Pesticides and herbicides are frequently found in streams draining agricultural land uses, with herbicides being the most commonly detected (McPherson et al. 2003, p. 44). Many agricultural streams still contain DDT and its degradation products (Zappia 2002, p. 50). Agricultural lands that surround occupied bridled darter habitat in Georgia have adopted “Roundup Ready” crops extensively. These GMOs were developed to survive applications of the herbicide Roundup and

23 their prevalent use in agriculture corresponds with an increased use of Roundup. “Roundup’s active ingredient is glyphosate, which impedes photosynthesis. Glyphosate is non-toxic to slightly toxic to most fish, although toxicity appears to be higher in several important sport or food fish, including brown trout, rainbow trout, channel catfish, bluegill, and tilapia (Kegley et al. 2016). Roundup it commonly is used in salt form (isopropylamine salt). This salt, as well as the surfactant normally found in Roundup (polyethoxylated tallowamine; POEA) and/or other ‘inert’ ingredients in the Roundup formulation appear more toxic to fish (Mitchell et al. 1987, p. 1032) and mussels than glyphosate alone, causing death of mussel glochidia (Bringolf et al. 2007, p. 2099) and subcellular and DNA changes that may affect survival (Szarek et al. 2000, p. 439; Cavalcante et al. 2008, p. 4; Langiano and Martinex 2008, p. 229). Temperature, pH, suspended sediment, and other water quality parameters may affect glyphosate and Roundup’s effects on aquatic species. Bridled darters exposed to agricultural chemicals likely experience stress and reduced fitness.

Livestock Access to Streams

Livestock (primarily cattle) is produced in all counties with streams occupied by the bridled darter. In Georgia, the mean number of cattle farms among six counties with bridled darter records is 115 (USDA 2014, p. 464). In Tennessee, the bridled darter occurs in Polk and Bradley counties which have 146 and 527 cattle farms respectively (USDA 2014, p. 371). On many cattle farms, livestock is grazed on pastures adjacent to streams and rivers occupied by bridled darters. In some cases, livestock is allowed free access to the water. Access to streams by cattle has a negative effect on water quality and habitat destruction. Of particular relevance, livestock accessing streams can introduce excess nutrients into streams, de-stabilize stream banks which creates increased sediment loads within streams (discussed below), and overgrazing can destroy natural riparian vegetation (discussed below).

Sedimentation

A wide range of current activities and land uses can lead to sedimentation within streams that can include: agricultural practices, construction activities, stormwater runoff, unpaved roads, forestry activities, utility crossings, and mining. Fine sediments are not only input into streams during presently ongoing activities, historical land use practices may have substantially altered hydrological and geological processes such that sediments continue to be input into streams for several decades after those activities cease (Harding et al. 1998, p. 14846).

The negative effects of increased sedimentation are well understood for aquatic species (Newcombe and MacDonald 1991, p.72; Burkhead et al. 1997, p 411; Burkhead and Jelks 2001, p. 964). Sedimentation can affect fish species by degrading physical habitat used for foraging, sheltering and spawning (Burkhead and Jelks 2001, p. 964; Sutherland 2005, p. 90), alter food webs and stream productivity (Schofield et al. 2004, p. 907), force altered behaviors (Sweka and Hartman 2003, p. 346), and even have sub-lethal effects and mortality on individual fish

(Sutherland 2005, p. 94; Wenger and Freeman 2007, p. 7). Chronic exposure to sediment has been shown to have negative impacts to fish gills, causing gill damage, stress, and may reduce growth rates (Sutherland and Meyer 2007, p. 401). Bridled darters may experience detrimental effects of sedimentation in the form of gill damage, reduced visibility for feeding and communication, decreased availability of suitable spawning habitats, and reduced spawning success as a result of fine sediments smothering and killing eggs.

Loss of Riparian Vegetation

For this assessment, loss of riparian vegetation refers to removal of natural plant communities from the riparian zone of rivers and streams. Where the bridled darter occurs, reduced or lost riparian vegetation is typically associated with lands used for agriculture or rapidly urbanizing lands. In these cases, the natural riparian plant community is often replaced with lawns, pasture land, or even impervious surfaces.

Removal of riparian vegetation can destabilize stream banks, increasing stream sedimentation and turbidity (Barling and Moore 1994, p. 544; Beeson and Doyle 1995, p. 989); reduce the stream’s capacity for trapping and removing contaminants and nutrients from runoff (Barling and Moore 1994, p. 555; Peterjohn and Correll 1984, p. 1473; Osborne and Kovacic 1993, p. 255; Vought et al. 1994, p. 346); increase water temperature (Brazier and Grown 1973, p. 4; Barton et al. 1985, p. 373; Pusey and Arthington 2003, p. 4); and increase light penetration to streams. In turn, this increases algae (primary production) (Noel et al. 1986, p. 667; Pusey and Arthington 2003, p. 6); reduces woody debris inputs, removing a source of aquatic habitat (Karr and Schlosser 1978, p. 231); and reduces leaf litter, therefore, decreasing overall stream production (Nakanao et al. 1999, p. 2440; Wallace et al. 1999, p. 429). Aquatic food webs are largely driven by inputs of organic matter from plant and other coarse material that is blown into the stream (Allan 1995, pg. 109), primarily from riparian zones.

Development practices associate with urbanization may remove all vegetation within the riparian zone. However, voluntary best management practices (BMPs) often involve maintaining riparian buffers (a width of land adjacent to a waterbody where vegetation is left in place). Buffers are an essential component of an overall program of stream ecosystem protections, however, studies that compared open and forested reaches in the Etowah basin along five small streams in suburban catchments (Roy et al. 2005, entire) concluded that riparian buffers – although necessary for protecting fish assemblages –were insufficient alone to maintain healthy assemblages in an urban setting where much stormwater runoff is transported to the stream in pipes, bypassing the buffer. Similarly, agricultural ditches that rapidly drain water from farm fields effectively bypass the filtering provided by a riparian zone with intact vegetation allowing for increased agricultural chemicals and nutrients to enter rivers and streams.

In summary, the bridled darter has adapted to occupy habitats that are surrounded by vegetation, in particular, overstory tree canopy. This riparian vegetation moderates temperature by blocking

solar radiation, provides a source for terrestrial plant material that forms the base of the food web and provided shelter and foraging habitat for the bridled darter, and helps to maintain clear, clean water and substrate through filtration. Loss of riparian vegetation is expected to decrease habitat suitability for the bridled darter.

Weather events

Weather events that effect stream flows are considered to be most relevant to the bridled darter in this assessment. Broadly, these events include extreme storms and droughts. Increased flows can cause physical washout of eggs and larval fishes, stress on adults (Freeman et al. 2001, p. 187; Power et al. 1996, p. 893), and alter the quantity and quality for primary and secondary production in an stream (Bunn and Arthington 2002, entire), indirectly affecting many fish species. Within the range of the bridled darter, extreme flows associated with hurricanes have been reported to have negative effects on stream fish populations (USFWS 2011, p. 9). Reduced baseflows due to droughts can cause population declines, habitat loss, reduced water quality (decreased dissolved oxygen and temperature alteration) leading to death, crowding of individuals leading to stress, and decreased reproduction in stream fish populations (Mathews and Mathews 2003 , p. 1237). Climate models for the southeastern United States project that average annual temperatures will increase, cold days will become less frequent, the freeze-free season will lengthen by up to a month, temperatures exceeding 95 degrees will increase, heat waves will become longer, and the number of category 5 hurricanes will increase (Ingram et al. 2013, p. 32). While these climate models predict variability into the future, they suggest that the region will be subjected to more frequent large storms (hurricanes) as well as low flows from droughts.

Figure 7. Influence diagram depicting how resource needs of the bridled darter are affected by land use practices and environmental conditions

Conservation Measures

The bridled darter is recognized by Georgia and Tennessee as a species of concern. It is listed as Endangered by the State of Georgia and Threatened by the State of Tennessee. In general, protections accorded to the bridled darter by the States prohibit direct exploitation of the species.

Within the Conasauga River basin, the Natural Resource Conservation Service (NRCS) has begun a Working Lands for Wildlife (WLFW) project that provides technical and financial assistance to help landowners improve water quality and help producers plan and implement a variety of conservation activities, or practices that benefit aquatic species. Bridled darter may benefit from water quality improvements in portions of the Conasauga River that are affected by agricultural practices as a result of the WLFW project.

Priority watersheds within the range of the Bridled darter have been designated as Stategic Habitat Units (SHUs) by the Alabama Rivers and Streams Network (ARSN). The SHU project was developed for species restoration and enhancement. The Oostanaula River watershed (which includes the Conasauga and Coosawattee River populations) and is occupied by bridled darter has been designated as a SHU.

Some populations of bridled darter are known from watersheds in which a substantial percentage of lands are owned and managed by the U.S. National Forest Service (NFS). These populations are found in the Conasauga River and upper Etowah River. In the Conasauga River, the majority of current records for the bridled darter are within the proclamation boundary of NFS lands. Cherokee National Forest in Tennessee, Chattahoochee National Forest in Georgia own and manage lands and natural resources in occupied watersheds in those portions of the bridled darter’s range. Management prescriptions implemented by the NFS in areas that overlap with the range of the bridled darter are expected to benefit the species. Specifically, a 4.5 mile reach of the Conasuaga River is eligible for Congressional Wild River designation and managed to protect and perpetuate the features that led to the eligibility status. The river is also recognized for its aquatic biodiversity by NFS and management strategies employed by both Cherokee and Chattahoochee National Forests within the watershed involve designated wilderness areas, recommended wild river, recommended recreational river, black bear habitat management, restoration and maintenance of rare communities, restoration/management of old growth characteristics, and scenic corridors and sensitive viewsheds among others. These management strategies that emphasize natural forest communities and water quality are expected to benefit bridled darter within the Conasauga River watershed. The Chattahoochee National Forest management prescriptions within the upper Etowah River also broadly emphasize and promote natural plant communities and as such are expected to benefit bridled darter within this watershed.

Within the Amicalola Creek watershed approximately 13.6 miles of the stream are protected by lands owned and managed by the State of Georgia. Among the stated management goals for these lands, maintenance or enhancement of populations of sensitive species and management of riparian areas to benefit water quality, aquatic resources, and aesthetics are expected to benefit bridled darters. Additionally, approximately 488 acres of the aforementioned state owned lands were purchased with the assistance of a Recovery Land Acquisition Grant that prioritized the conservation of aquatic resources and species. Therefore, it is anticipated that State ownership and management within the Amicalola Creek watershed will benefit the long-term survival of bridled darter.

Chapter 5: Current Watershed and Population Conditions

Current habitat and population conditions are described below. This section details specific stressors acting within the occupied watershed. Additionally, collection history and qualitative abundance is provided. Current population resiliency is assessed for each watershed specifically, followed by a summary of range wide redundancy and representation.

To qualitatively assess current viability we considered five components that broadly relate to either the physical environment (“Habitat Elements”) or characteristics about the population specifically (“Population Elements”). Habitat elements consisted of an assessment of physical habitat, connectivity, water quality, and hydrologic regime. Population elements consisted of an estimation of approximate abundance, the extent of occurrence (total length of occupied streams), and an assessment of occurrence complexity. We further defined how each of these components might vary in terms of condition (see Table 2). An overall resiliency condition was estimated by combing habitat and population elements. Population elements were weighted 2X higher than habitat elements because they are considered direct indicators of population condition. Conditions were classified as “Low”, “Moderate”, or “High”. To help visualize variability that exists within each condition category, we utilized a simple color ramp when displaying overall population resiliency. This color ramp is only intended as a visual aid to highlight populations that vary in resiliency even though the final resiliency condition categories (low, moderate, high) are equivalent.

Low Moderate High

Figure 8. Example color ramp that visualizes variability found within each resiliency condition category.

METHODS

Population Elements

To assess population elements, collection records from natural history museums and field notes (when available) were evaluated. Collection records were compiled and provided to the Service by state partners funded under a concurrent Section 6 status assessment for the bridled darter. The dataset used in this analysis is not considered to be exhaustive, but represents the best data accessible in the public domain. Each collection record is georeferenced with geographic coordinates. These records were considered recent if they represented a collection within the last 10 years (2007 or more recent) and historical if they represented a collection prior to 2007.

Collection records did not exhibit standardization. The number of individuals collected was inconsistently recorded and sampling methods varied among records. Therefore, we did not

analyze numbers collected for each record. Instead, abundance was estimated for each record categorically. Two categories were used to assess whether a record represented a “rare” (1-10 individuals) collection or a “common” (10-100 individuals) collection. The percentage of rare and common collections within a population was used to assess population level abundance. In some cases, “present” was the only value associated with collection number. These records were not considered in our qualitative abundance estimations.

Occurrence extent for the bridled darter was evaluated by measuring the distance between the furthest upstream record and the furthest downstream record. Historical and current records were assessed separately to quantify any range reduction that may have occurred.

Occurrence complexity is a measure of the spatial complexity of the occupied habitat. For aquatic species that inhabit rivers, complex spatial occurrence would relate to a species occupying multiple tributaries and the main-stem river as opposed to only inhabiting the main- stem river. If good connectivity is assumed, than the more complex and dendritic (tree-like) spatial arrangement of occupied habitat will be more resilient against extinction (Fagan 2002, p. 3244). We considered high occurrence complexity to exist when individuals occupied the main- stem river in addition to more than three major tributaries. Low occurrence complexity would exist if a species only inhabited the main-stem river and up to two tributaries.

When assessing components of resiliency, we consider population elements to be a more direct indicator of resiliency condition than habitat elements. Therefore, population elements are weighted 2x higher than habitat elements in our resiliency assessment.

Habitat Elements

Population abundance, spatial extent and spatial complexity are results of successful spawning, recruitment (survival of young individuals to maturity and spawning), adult survival, and dispersal. These population dynamics are related to the “needs” of a species which correspond to water quality, water quantity, structural habitat, and connectivity for the bridled darter (discussed in more detail in Chapter 3 of this document). Therefore, it is useful to consider habitat elements when assessing the condition of a population.

Physical (structural) habitat was assessed with spatial data. Specifically, land cover and use was evaluated within the Active River Area (ARA) of each occupied watershed. The ARA was developed to provide a more meaningful method for assessing riparian zones than a simple buffer. It encompasses the dynamic processes within the aquatic and riparian zones that interact with a lotic system and create the associated habitats and habitat conditions (Smith et al. 2008, pg. 1). The percentage of natural vegetation within the ARA was used as an indicator of within stream habitat quality. Land cover types considered as natural include open water, deciduous forest, mixed forest, shrub, wooded wetland and herbaceous wetland. For this analysis, the evergreen forest land cover type was considered as altered vegetation because this likely represents silviculture within the range of the bridled darter. In addition to vegetation types

within the ARA, we assessed other land use practices that may affect in stream habitat quality (e.g. cattle access to streams, extent of urban areas outside of ARA, channelization, etc.).

Connectivity was assessed by evaluating the number and placement of small and large dams within populations of bridled darter and across its range. Road crossings and culverts that act as barriers were not considered to be a relevant source of decreased connectivity and were not considered in this analysis. This is because the bridled darter inhabits streams that are typically too large to be spanned by culverts.

Water quality conditions within populations of bridled darter were determined by assessing known and reported water quality issues from the Environmental Protection Agency’s Clean Water Act Section 303(d) and Total Maximum Daily Loads (TMDLs) program. When available, watershed reports by non-governmental organizations (NGOs) were also used to assess water quality. Additionally, we assessed the prevalence of land use practices that are known to negatively affect water quality (e.g. poultry houses and urban areas) when determine water quality conditions.

To assess hydrologic regime conditions within populations of bridled darter, any land use or resource use practice that is known to affect flows and occurred within the occupied watershed was considered. These practices were related to urbanization, agriculture, and reservoir construction. Any of these practices can cause deviations from a more natural flow regime and have negative effects on bridled darter as discussed in Chapter 3.

Table 2. Definitions of conditions for components used to assess current conditions

High Medium Low 0 Physical Habitat No known Known low level Habitat heavily Unable to support alteration alterations to altered and survival occurring within habitat but not recognized as Active River Area known to be impacting species, (ARA),> 90% negatively <50% natural natural veg affecting species, vegetation in ARA natural vegetation 50-89% in ARA

Connectivity No known barriers Passage barriers Passage barriers Unable to support to fish passage known but do not identified as survival impact species negatively affecting populations

Water Quality Minimal or no Issues recognized WQ issues known Unable to support known water (i.e. 303d streams, to impact survival quality issues unpaved roads, populations moderate housing amounts)

Hydrologic Regime Minimal or no Issues recognized Flow issues known Unable to support known flow issues but low intensity to impact species survival (lower density (hydropeaking, suburban water avail issues development, below reservoirs) lower amounts of channelization)

Approximate >75% of 75-50% of >50% of Extirpated Abundance collections collections collections classified as classified as classified as rare common (10-100 common (10-100 (1-10 individuals) individuals) individuals)

Occurrence Extent Entire known <30% decline from >30% decline in Extirpated range currently known range known range occupied

Occurrence Occupies main Occupies main Occupies main Extirpated Complexity channel and channel and channel and mouths numerous maximum of 3 of a maximum of 2 tributaries tributaries tributaries

Representation

To evaluate representation for the bridled darter, we considered the variability that has been documented within the species (genetic, morphological, and behavioral). The aforementioned variability has been found in the Etowah and Conasauga rivers, but has not been identified in other occupied populations. Therefore, we consider watershed variability as a component of representation as it can correlate with genetic, morphological, or behavioral variability within aquatic species. We also consider variability in the species’ ecological setting in which the species has evolved by assessing occupied physiographic provinces. Finally, we consider connectivity when assessing representation. Lack of connectivity among populations would prevent the exchange of novel and beneficial adaptations or prevent migrations to more suitable habitat. Therefore, without connectivity, the species’ ability to adapt to a changing environment is lost even if representative populations persist.

The potential ranges of variability were qualitatively classified into condition categories that represent “Medium” and “Low” representation (Table 3). The bridled darter is an endemic species to the upper Coosa River basin and occupies a narrow range (six populations). Little natural variability is observed in this small range sizes. Therefore, we make the assertion that the bridled darter would not naturally display “High” representation in terms of watershed variability, genetic, morphological, and behavioral variability, or physiographic province variability. To clarify, it is helpful to consider representation that is lost if extirpation occurs within a population. If the bridled darter is extirpated from one physiographic province, this represents a 33% reduction in variability of ecological setting. Extirpation from a single watershed represents a 16% reduction in watershed variability. Extirpation within the Conasauga or Etowah rivers would represent a 50% reduction in identified genetic, morphological, and behavioral variability.

Table 3. Definitions of condition categories for representation

High Medium Low Physiographic * All provinces One or two provinces Province Variability occupied with high occupied high resiliency, populations resiliency, populations Watershed * >75% of watersheds <75% of watersheds Variability with known records with known records maintain extant, high maintain an extant, resiliency, populations high resiliency, population Genetic, * Extant populations Variation is lost due Morphological, that represent all to extirpation in either Behavioral known genetic, the Conasauga or Variability morphological, and Etowah rivers behavioral variability

Redundancy

Redundancy for the bridled darter is characterized by having multiple, resilient and representative populations distributed throughout its range. Similar to representation, we consider the small range of this endemic species when evaluating redundancy. The bridled darter is effectively known from six populations. Therefore, we make the assertion that the bridled darter would not naturally display “High” redundancy because the loss of any one population would represent an approximate 16% reduction in total redundancy.

In this assessment, we consider the bridled darter to intrinsically have “Medium” redundancy and that this condition can be maintained if five of the six populations are found to have a “High” resiliency. We also consider connectivity when evaluating redundancy. Connectivity would allow for dispersal and recolonization events to occur should a population become extirpated within a watershed (rescue effect). Without connectivity the relative importance of localized stochastic events is increased. In other words, as isolated populations become extirpated, the species as a whole is less robust to smaller, more probable, and potentially more frequent stochastic events.

CURRENT CONDITION

Conasauga River

Current records (those made since 2007) for the bridled darter exist in the Conasauga River from the southern end of the Alaculsy Valley in Georgia to the TN Hwy 74 Bridge crossing on the border of Bradley and Polk County, Tennessee. The bridled darter has also been observed in the downstream portions of some larger tributaries to the Conasauga River such as Jacks River, Minnewauga Creek, and Ballplay Creek. The total currently occupied reach length in the Conasauga River watershed is approximately 20 river miles (~33 river kilometers). This reach length represents 66% of the historical known range of the bridled darter in the Conasauga River watershed. The furthest downstream record for the bridled darter consists of a single specimen collected in 2005, downstream of Tibbs Bridge Road approximately 6.5 miles ESE from Dalton, GA. Numerous surveys between Tibbs Bridge Road and TN Hwy 74 have not recorded bridled darter. Therefore, the historical range is not extended to this downstream most site. The Tibbs Bridge Rd record potentially represents a downstream dispersal event or a waif.

The majority of collection records (~61%) were found to be “rare”, or less than 10 individuals were collected. The spatial arrangement of occurrence records is generally a simple linear arrangement. Although the bridled darter does occur in some tributaries to the Conasauga River, these occurrence records are in short segments of the lower reaches and do not appreciably contribute to an overall complex occurrence extent.

The majority of current records for this species are upstream of the US 411 bridge in Polk County, TN. Much of the surrounding land in this portion of the watershed is owned by the U.S. Forest Service and is noted for having good water quality and suitable habitat, although unpaved forestry roads are a source of increased levels of sedimentation.

Downstream of the U.S. 411 Bridge, the majority of the surrounding lands are privately owned and used for agriculture and some low-intensity development. Physical habitat degrades with increases in bank erosion, sedimentation, and turbidity. Water quality also begins to diminish in this portion of the watershed. Pollutants from agricultural runoff have degraded water quality in the main stem Conasauga. Crops along the Conasauga River are mostly genetically modified to be "Roundup Ready". This has led to increases in spraying of glyphosate and surfactants. Declines of sensitive species within the Conasauaga River have been found to correlate with the wide adoption of glyphosate resistant crops and the associate spreading of the herbicide and its surfactants (Robin Goodloe pers comm 2017). Poultry farming is prevalent and spreading of chicken litter is common. As a result, high levels of endocrine disruptors are present in the Conasauga River and its tributaries. Agricultural fields along the Conasauga River have also been ditched to rapidly move water off of the fields. These agricultural ditches bypass natural filtration that may occur within a naturally vegetated riparian zone and create a direct discharge of agricultural pollutants and sediments into the Conasauga River.

Water quality monitoring in the Conasauga River since 1997 shows an increasing trend in nitrite (NO2) and nitrate (NO3) concentration and comparatively higher concentrations of total nitrogen in 2011-2012 than 1999-2000 (Hagler and Freeman 2012, p. 42). Nitrogen concentrations are consistently elevated above the EPA’s reference criteria for Ridge and Valley streams. In contrast, soluble reactive phosphorus (SRP) and total phosphorus concentrations have been lower in recent years that from 1997-2000, although the strong trend in the downstream reach may overshadow more subtle differences in other reaches. Low flows and drought in the Conasauga River in recent years may have contributed to lower mean SRP concentrations, since phosphorus cycling in stream is largely driven by precipitation events. In general, nutrient concentrations in the tributaries are much greater than those in the main-stem. The three tributaries (Perry, Sumac, and Mill (GA)) with the highest NO2 and NO3 concentrations also had the lowest SRP concentrations (Hagler and Freeman 2012, p. 42).

Increasing nutrient concentrations, especially nitrogen, suggests eutrophication may be a major stressor for biota in the Conasauga River (Hagler and Freeman 2012, p. 46, Baker et al. 2013, p. 8). Eutrophication, where nutrient concentrations have exceeded some threshold and nutrient supply is greater than the river’s assimilative capacity, is associated with deteriorating water quality and diminished species diversity. Evidence of a state change to potential eutrophic conditions beginning within a 10 km reach just downstream of the National Forest boundary has been observed, based on the results of a nutrient-diffusing substrate experiment and increases in algal production (Baker et al. 2013, p. 2).

The Conasauga River that flows through private lands may benefit from a new Natural Resource Conservation Service (NRCS) Working Lands for Wildlife (WLFW) partnership that will help farmers develop and implement strategies to improve water quality. While this partnership will help conserve the river and its biota, it is known that restoration actions can take decades before aquatic faunal assemblages return to a natural state (Harding et al. 1998, 14845).

Because of the pervasive water quality issues in the middle and lower Conasauga River, lower abundance of fish per collection record, a small and reduced distribution, and overall low spatial complexity in the Conasauga River, this population is considered to have a low resiliency to stochastic events with the portion of the population upstream of the U.S. 411 crossing and within the National Forest boundary to have the greatest probability of persistence. This portion of the Conasauga River also likely represents the upstream terminus of the population and the Bridled darter is not expected to move further upstream, out of the Alaculsy Valley or into upstream tributaries.

Low Moderate High X Figure 9. Final resiliency condition for the Conasauga River population

Figure 10. Historical and current distribution of bridled dater in the Conasauga River

Holly Creek

Current records (as of 2007) for the Bridled darter exist in Holly Creek approximately from its confluence with Lead Mine Branch to the bridge crossing at Tom Terry Road in Murray County, GA. The furthest downstream occurrence is a historical record adjacent to the town of Chatsworth, GA. The Bridled darter’s current range is approximately 6 river miles (10 km) and represents 66% of its historically known range in the watershed. The majority (63%) of collections made in Holly Creek found the Bridled darter to be common (10-100 collected), although only 9 records for this species exist here. Records for this species are entirely within Holly Creek and this population exhibits low spatial complexity for its distribution.

Water quality declines in Holly Creek around Chatsworth and experiences some flashiness due to the increased amounts of impervious surfaces. Pasture land surrounds other portions of Holly Creek which allow for some cattle access and causes bank erosion and increases in sedimentation. Like much of North Georgia, poultry farms are present in the watershed and litter

37 is spread onto nearby pastures that are adjacent to Holly Creek. Increased nutrient levels and concentrations of endocrine disruptors are anticipated from the poultry litter. However, there are fewer poultry farms here than in other parts of the region. Residential development in the upstream portions of this river has been identified as causing increases in sedimentation and turbidity (USFWS 2014, p. 10). These stressors in addition to the small extent and complexity of occurrence records suggest that bridled darters in Holly Creek have a low resiliency to stochastic events.

Low Moderate High X Figure 11. Final resiliency condition for the Holly Creek population

Figure 12. Historical and current distribution of bridled dater in Holly Creek

Talking Rock Creek

Within the Talking Rock Creek watershed, the Bridled darter has been collected four times from widely scattered locations from Talona Creek at Carns Mill Rd downstream to Talking Rock Creek approximately at the Pickens-Gilmer County line in Georgia over a distance of about 15 river miles (24 km). Current records exist for the full extent of the species known occurrences in this watershed, although all records found the Bridled darter to be rare. The spatial arrangement of occurrence records is a straight line from the upstream to downstream record, indicating low complexity for this population’s distribution.

Two limestone quarries are present along Talona Creek and have the potential to increase sedimentation and alter water chemistry within Talona Creek and Talking Rock Creek. The Georgia Environmental Protection Department (EPD) has identified portions of Talking Rock Creek and its tributaries to be "non-supporting" for fishing and named negative effects of nonpoint source pollution on fish communities as the source. The nonpoint source pollution potentially originates from low level developments and agricultural fields and pastures. Poultry houses are present in this watershed and pastures are spread with chicken litter increasing nutrient and endocrine disruptor concentrations. Upper portions of Talking Rock Creek that flow through pasture land have little or no natural vegetation in the riparian zone and experience bank erosion and increased levels of sedimentation. Sedimentation, nutrient pollution, riparian alteration from forestry and agriculture, and urbanization has been identified to negatively affect water quality (Albanese et al. 2013, pp. 347-348).

Fish populations in Talking Rock creek are completely isolated from the Coosawattee and the rest of the Upper Coosa River basin by a reregulation reservoir associated with Carters Dam. Water impounded from the reregulation dam backs into Talking Rock Creek and eliminates suitable habitat for the Bridled Darter from the lower reaches of the stream. Small reservoirs upstream of the town of Talking Rock prevent upstream movement.

Two hypotheses have been proposed to explain the apparent rarity of sensitive fish species in Talking Rock Creek (Albanese et al. 2013, p. 356). Talking Rock Creek begins in the Blue Ridge geographic province and rapidly moves into Ridge and Valley where it has a lower gradient than the other streams in the region that are occupied by Bridled Darter. The rapid change in geology and elevation suggest that Talking Rock Creek may have historically provided less suitable habitat and behaved as a sink population (a population where death rates exceed birth rates) and would have been naturally maintained through immigration from a source population (a population where birth rates exceed death rates). Alternatively, river and land use alteration may have degraded water quality and habitat and led to the apparent decline of bridled darter and other sensitive fish species (blue shiner, goldline dater, and bridled darter) in Talking Rock Creek. Lack of connectivity between this population and others prevents any natural immigration into Talking Rock Creek from occurring and increases the risk of extirpation.

Due to identified water quality issues, the overall low abundance of bridled darters in this system, the low spatial complexity of occurrences, and lack of connectivity, this population has a low resiliency to stochastic events. Georgia DNR found this population to currently be at a high risk of extirpation (Albanese and Abouhamdan 2017, p. 9).

Low Moderate High X Figure 13. Final resiliency condition for the Talking Rock Creek population

Figure 14. Historical and current distribution of bridled dater in the Talking Rock Creek

Long Swamp Creek

Bridled Darters have been collected from Champion Creek at Old Grandview Road downstream to Long Swamp Creek at GA HWY 53. Current records exist from Long Swamp Creek approximately at Cove Road to Long Swamp Creek at GA HWY 53. The Bridled Darter’s current distribution in Long Swamp Creek comprises about 5 river miles (8 km) of Long Swamp Creek and represents about 62% of its historical distribution in this watershed. A small run-of- river dam is located upstream of Cove Road that prevents fish passage and effectively fragments

the population of Bridled Darters in Long Swamp Creek. Additionally, a dam on Champion Creek (creating Grandview Lake) prevents any further upstream movement.

Since 2007, Bridled Darters have been collected five times. Each record found the Bridled Darter to be rare (<10 individuals per record). In a total of six separate surveys efforts to locate Bridled Darters in the watershed by Georgia DNR in the summer of 2016, a single individual was found. In addition to a low abundance and small distribution in the watershed, this population also exhibits low spatial complexity because occurrences are oriented in a straight line from Champion Creek to the downstream point on Long Swamp Creek.

Marble quarries downstream of GA Hwy 53 located alongside Long Swamp Creek and adjacent to East Branch Long Swamp Creek along GA Hwy 53 have the potential to increase sedimentation and degraded habitat quality in the downstream portions of each stream. Upstream of GA Hwy 53 are some agricultural pastures and poultry farms. Some pastures adjacent to Long Swamp Creek have little or no natural vegetation in the riparian zone. At these locations there is bank instability, erosion, and increases in sedimentation and associated degraded physical habitat. The Georgia EPD has identified several streams that have degraded water quality within this watershed.

This population has a low resiliency to stochastic events due to low abundance of Bridled Darter per collection, small population range size, a large barrier that fragments this population, low spatial complexity in the occupied range, and factors that degrade habitat or water quality. Georgia DNR also found this population to currently be at a high risk of extirpation (Albanese and Abouhamdan 2017, p. 9).

Low Moderate High X Figure 15. Final resiliency condition for the Long Swamp Creek population

Figure 16. Historical and current distribution of bridled dater in the Longswamp Creek

Amicalola Creek

Within the Amicalola Creek watershed, the Bridled darter has been collected from Amicalola, Little Amicalola, and Cochran creeks for approximately 20 river miles (32 km). Current records (those made since 2007) are from Amicalola and Little Amicalola Creeks with a range size of about 7 river miles (11 km) which represents about 34% of its historical range size. The majority (59%) of recent records found the bridled darter to be “common” (10-100 individuals per collection) with about 40 records existing within this watershed. Because current records for this population exist only within Amicalola Creek and a single major tributary, occurrence spatial complexity is low.

Many of the same stressors that are present in other North Georgia streams exist in the Amicalola watershed. Some major tributaries have been channelized during past agricultural practices and experienced a reduced amount of suitable habitat and decreased stream residence times (increased flashiness) as a result. Chicken farms are present in this watershed and some pasturelands adjacent to occupied streams receive chicken litter from poultry farming practices. Small impoundments at the headwaters of occupied streams prevent upstream movement of Bridled Darter. Approximately 46.7 km of Amicalola Creek are owned by the state of Georgia and managed as Dawson Forest Wildlife Management Area (WMA). While the WMA does afford some protection, the Georgia State Wildlife Action Plan (SWAP) notes that residential developments within the watershed are negatively affecting aquatic habitats (GA DNR 2015, p. 88).

While state ownership of adjacent lands provide some protection and help maintain water quality and physical habitat this population has undergone a substantial range reduction, occupies a small area, and exhibits low spatial complexity. Therefore, it is expected to have a low resiliency to stochastic events.

Low Moderate High X Figure 17. Final resiliency condition for the Amicalola Creek population

Figure 18. Historical and current distribution of bridled dater in Amicalola Creek

Etowah River

Within the Etowah River basin, the Bridled Darter has been collected from an upstream-most site in the Etowah River at Hightower Church Rd downstream to about 0.6 air miles (~1 km) upstream of the mouth of Amicalola Creek. Current records exist for the species from the Etowah River at the upper Hightower Church Road crossing to the Etowah River at Castleberry Bridge Road, a distance of about 21 river miles (~33 km) which represents approximately 49% of its historical range in the watershed. Because records are only known from the Etowah River in this watershed, it exhibits low spatial complexity. Bridled darters have been collected 37 times in the last ten years in the Etowah River and 90% of these records found the species to be rare (less than 10 individuals per collection).

The upper portions of the watershed are within Chattahoochee National Forest and wildlife management areas managed by Georgia Department of Natural Resources. This part of the Etowah River basin is largely forest cover (~75% natural vegetation in the active river area). Low intensity developments in some parts of the watershed can negatively affect water quality from leaky septic systems and storm water. As with other parts of North Georgia, chicken farms are present and spreading of litter occurs on pastures adjacent to the Etowah River. However, there are fewer open agricultural lands here than in other watersheds occupied by Bridled Darter. Sedimentation from non-paved roads is present. In general, this watershed has good water quality, adequate flows, and suitable habitat. However, because the Etowah River population was found to have low qualitative abundance, low spatial complexity of occurrence, and low extent of occurrence the Etowah population is expected to have a low resiliency to stochastic events.

Low Moderate High X Figure 19. Final resiliency condition for the Etowah River population

Figure 20. Historical and current distribution of bridled dater in the Etowah River

Table 4. Estimated current resiliency factors and overall resiliency condition for bridled darter populations

Approximate Occurrence Occurrence Physical Connectivity Water Hydrologic Overall Abundance Extent Complexity Habitat Quality Regime Condition Conasuaga Low Low Low Moderate High Low Moderate Low River (45 collections) Holly Creek Moderate Low Low Moderate High Low Moderate Low (10 collections) Talking Rock Low High Low Moderate Low Low Moderate Low Creek (4 collections) Long Swamp Low Low Low Low Low Low Low Low Creek (5 collections) Amicalola Moderate Low Low Moderate Moderate Moderate Moderate Low Creek (39 collections) Etowah River Low Low Low Moderate High Moderate High Low (37 collections)

Current Species Representation

Currently, all historically occupied physiographic provinces are occupied, albeit with populations with low resiliency; therefore, physiographic province representation is low. Similarly, because all populations exhibit low resiliency, watershed variability is low even though all historically occupied watershed remain occupied. Finally, although populations that exhibit the known genetic, morphological, and behavioral variability are currently extant, they do not exhibit high resiliency. Therefore, genetic, morphological, and behavioral representation is considered low.

Connectivity is an important aspect of representation because it provides for the exchange of novel and beneficial adaptations and migration to more suitable habitat (should it be necessary). Connectivity is reduced for the species, range-wide. Dams have completely isolated the six populations into three groups. The upper Etowah River-Amicalola Creek-lower Longswamp Creek populations are isolated by Alatoona Dam and the Talking Rock Creek population is isolated by Carters Re-regulation dam. The Conasauga River and Holly Creek populations are prevented from dispersing in to the other populations by those same dams. Where dams do not fragment habitat, long reaches of unoccupied habitat are present between populations; indicating that migration between populations is uncommon or unlikely.

Finally, all populations of bridled darter exist on the periphery of the Coosa River basin and have likely reached the upstream limits for the species. It is unlikely that individuals within a population will be able to migrate further upstream if necessitated by changes in environmental conditions, further decreasing the “ability of the species to adapt to changing environmental conditions”.

We estimate that the bridled barter currently has low adaptive potential due to limited representation in six occupied watersheds, lack of connectivity, and confinement to upper reaches of occupied watershed. Overall representation for the bridled darter is low.

Current Species Redundancy

Redundancy for the bridled darter is characterized by having multiple, resilient and representative populations distributed throughout its range. Because all populations of bridled darter exhibit low resiliency, the species is considered to also have low redundancy. All

population have experience declines, low numbers, and/or have low spatial complexity. Connectivity is also reduced for the species, range-wide. Dams have completely isolated the six populations into three groups. The upper Etowah River-Amicalola Creek-lower Longswamp Creek populations are isolated by Alatoona Dam and the Talking Rock Creek population is isolated by Carters Re-regulation dam. The Conasauga River and Holly Creek populations are prevented from dispersing in to the other populations by those same dams named above. Where dams do not fragment habitat, long reaches of unoccupied habitat are present between populations; indicating that migration between populations is uncommon or unlikely. As mentioned earlier, the overall lack of connectivity between populations increases the importance of localized stochastic events and the species as a whole is less robust to smaller, more probable, and potentially more frequent stochastic events. Therefore, a key component of resiliency – the minimization of the effect of localized extirpation – is not met.

Chapter 6: Future Viability

In this chapter, we describe how current viability of the Bridled Darter may change over a period of 50 years. Like current conditions, we evaluate species viability in terms of resiliency at the population scale, and representation and redundancy at the species scale (3Rs). Here we describe three plausible future scenarios and whether there will be a change, from current conditions, to any of the 3 Rs under each scenario. Our future scenarios differ by considering variations that are predicted in two main elements of change, urbanization and climate. These scenarios capture the range of likely viability outcomes that the Bridled Darter will exhibit by the end of 2070.

The Human population in the southeastern United States has grown at an average rate of 36.7% since 2000, making it the fastest growing region in the country (U.S. Census 2016, p. 1-4). The Bridled Darter has been exposed to this reality because it inhabits small rivers of the upper Coosa River basin that are in close proximity to Atlanta, one of the largest metropolitan areas in the Southeast. As a result, urbanization has consistently been identified as a major stressor to this species and its habitat. Growth will continue at a rapid pace within Atlanta and the surrounding areas. Therefore, development and urban sprawl is expected to expand and influence areas that previously were unaffected by urbanization. Rapid growth in the Atlanta area and across the southeastern U.S. as a whole is expected to be a major driver of change and an important consideration when evaluating future viability of the Bridled Darter. In this section, we consider how land use across the Bridled Darter’s range is predicted to change and develop. Further, we assess how this increase in developed areas affects populations and the species as a whole.

Methods

To forecast future urbanization, we consider future scenarios that incorporate the SLEUTH (Slope, Land use, Excluded area, Urban area, Transportation, Hillside area) model. This model simulates patterns of urban expansion that are consistent with spatial observations of past urban growth and transportation networks, including the sprawling, fragmented, “leapfrog” development that has been dominant in the southeastern U.S. (Terando et al. 2014, p. 2). The extent of urbanized areas has been predicted to increase across the southeastern U.S. by approximately 100 – 192 % based on the “business-as-usual” (BAU) scenario that expects future development to match current development rates (Terando et al. 2014, p. 1). We use this range of percent change in urbanization to develop our future scenarios.

The Fifth Assessment Report (AR5) by the Intergovernmental Panel on Climate Change (IPCC) found that “continued emission of greenhouse gases will cause further warming and long-lasting changes in all components of the climate system, increasing the likelihood of severe, pervasive and irreversible impacts for people and ecosystems” (IPCC 2013, p. 8). Therefore, we expect climate change to be a driver of change that should be addressed when evaluating future viability of the Bridled Darter.

The IPCC utilized a suite of alternative scenarios in the AR5 to make near-term and long-term climate projections. These scenarios, called “representative concentration pathways” (RCPs) are plausible pathways toward reaching a target radiative forcing (the change in energy in the atmosphere due to greenhouse gases) by the year 2100 (Moss et al. 2010, p. 752). RCPs help scientists capture the most plausible range of outcomes for climate futures based on uncertainties inherent in the natural and socio-economic environment. In this assessment, we used RCPs to help understand how climate may change in the future and what effects may be observed that impact the Bridled Darter in the upper Coosa River basin.

There are four RCPs (Table 2) that have been utilized by the IPCC. These RCPs correspond to a high radiative forcing trajectory pathway (RCP8.5), a low radiative forcing trajectory (RC2.6), and two intermediate radiative forcing trajectories (RCP6.0 and RCP4.5). We used these RCPs as the basis for developing future scenarios with low, moderate, and high probabilities of extreme weather events as a result of low levels of climate change (RCP2.6), moderate level of climate change (RCP6.0-RCP4.5), and extremely altered climate conditions (RCP8.5), respectively.

Name Radiative forcing Concentration (ppm) Pathway -2 RCP8.5 >8.5 W m in 2100 >1,370 CO2-equiv in 2100 Rising without stabilization

-2 RCP6.0 ~6 W m at ~850 CO2-equiv (at Stabilization without stabilization after 2100 stabilization after 2100) overshoot

-2 RCP4.5 ~4.5 W m at ~650 CO2-equiv (at Stabilization without stabilization after 2100 stabilization after 2100) overshoot

-2 RCP2.6 Peak at ~3 W m Peak at ~490 CO2-equiv Peak and decline before 2100 and then before 2100 and then declines declines

Table 5. description of the four RCPs from Moss et al. 2010 pg. 753, please consult Moss et al. 2010 and Collins et al. 2013 for detailed descriptions of future climate scenarios.

In the Southeast through the 21st century, climate models project that average annual temperatures will increase, cold days will become less frequent, the freeze-free season will lengthen by up to a month, temperatures exceeding 95 F will increase, heat waves will become longer, sea levels will rise an average of 3 feet, the number of category 5 hurricanes will increase, and air quality will decline (Ingram et al. 2013). Aquatic systems will be impacted by increasing water temperatures, decreasing dissolved oxygen levels, altered streamflow patterns, increased demand for water storage and conveyance structures, and increasing toxicity of pollutants (Ficke 2007, p. 585, 586, 589; Rahel and Olden 2008, p. 522 and 526). Reduced spring/summer rainfall, coupled with increased evapotranspiration and water demand, could lead to local extirpations if streams dry out more frequently (Ingram et al. 2013). Regardless of RCP

and scenario evaluated, we anticipate some or all of events to occur. We attempt to capture the range of plausible climate outcomes by considering that the frequency and probability of extreme climate scenarios will be greatest under RCP8.5, minimal under RCP2.6, and intermediate under RCP6.0 and RCP4.5. For instance, we assume there will be a greater likelihood of a category 5 hurricane negatively impacting the Bridled Darter under RCP8.5 than under RCP2.6, RCP4.5, or RCP6.0.

Status Quo

In the Status Quo Scenario, current environmental regulations and policy, land use management techniques, and conservations measures remain the same over the next 50 years. We anticipate the current trend in greenhouse gas emissions to continue and moderate impacts from extreme weather events including intense drought, floods, and storm events to occur. Rapid urbanization will continue at the current estimated rate for the piedmont region of the southeastern U.S. (~165 % growth, Terando et al. p. 5) which will increase demand for water resources and introduce multiple additional stressors into local streams and rivers (see p. 14 in this document). Despite an overall growth in population and increases in developed areas, some regions will remain predominantly in agriculture and experience associated water quality declines. In pace with current trends we anticipate declines in habitat and water quantity and quality as a result of rapid urbanization, climate change, agricultural practices, and an overall lack of voluntary conservation measures being implemented.

Conasauga River

According to the SLEUTH model, urbanization is expected to increase slightly within the upper Conasauga River but substantially more around Dalton, Georgia. Development will begin to merge the cities of Dalton and Chatsworth, Georgia. Areas that are not developed will remain in agriculture. Under the Status Quo scenario, agricultural practices are expected to remain consistent with those of today. Therefore, we expect continued inputs of pollutants from herbicide applications, excess nutrients and endocrine disruptors from chicken farming and chicken litter spreading on pastures and fields adjacent to the Conasauga River, and increases in sedimentation. Due to water quality and physical habitat that has further degraded from current levels in the Conasauga River adjacent to private lands, we expect the bridled darter to be extirpated from these reaches but persist in upper reaches owned and managed by the U.S. Forest Service. This substantial loss of occupied range will lead bridled darter to have low resiliency in the Conasauga River by the end of 2070.

Low Moderate High X Figure 21. Final resiliency condition for the Conasauga River population

Figure 22. Predicted areas of urbanization within the Conasauga River

Holly Creek

Urbanization is expected to increase in and around Chatsworth, Georgia, expand westward toward Dalton, Georgia and northward along Holly Creek. The expansion of urbanization is expected to negatively affect water quality and quantity in the middle and lower reaches of Holly Creek. Sedimentation from construction practices as the watershed becomes more developed is expected to degrade physical habitat. Land surrounding developed areas is expected to continue to be used for agriculture. Within these areas, poorly vegetated riparian zones and the practice of spreading poultry litter will continue to input fine sediments, excess nutrients, and endocrine disruptors into Holly Creek. The entire Holly Creek population is anticipated to experience increases in exposure to stressors from agriculture and development under the Status Quo scenario. Therefore, under this scenario the bridled darter is expected to have very low resiliency and be at high risk of extirpation.

Low Moderate High X Figure 23. Final resiliency condition for the Holly Creek population

Figure 24. Predicted areas of urbanization within the Holly Creek

Talking Rock Creek

Currently, the population of bridled darter exhibits very low resiliency and has been found to be at risk of extirpation because of low abundance with five individuals being observed within the stream since 2007. It is not expected that this population will be able to withstand further habitat degradation from urbanization within this watershed and moderate increases in extreme climatic events are expected in this scenario. This population is likely to become extirpated under the status quo scenario.

Figure 25. Predicted areas of urbanization within Talking Rock Creek

Long Swamp Creek

Long Swamp Creek will see substantially more development around the towns of Jasper and Nelson, Georgia. The added pressures of urbanization will continue to degrade water and physical habitat quality and alter flows in this watershed. Mines and agricultural practices that remain will further contribute to degraded water quality. The population of bridled darter within Long Swamp Creek currently has very low resiliency due to low abundance and small occurrence extent and is not expected to persist with additional urban growth. Under the Status Quo scenario this small, isolated population will be likely extirpated.

Figure 26. Predicted areas of urbanization within Long Swamp Creek

Amicalola Creek

Development is expected to increase within the watershed primarily along Cochran Creek according to the SLEUTH model. Increases in development will reduce water and habitat quality. Agricultural practices are likely to contribute to reductions in water and habitat quality. Because much of the Amicalola Creek corridor is owned and managed by the State of Georgia effects from both urbanization and agriculture are anticipated to be minimized. Therefore, under the status quo scenario, this population is expected to persist and maintain a low resiliency to stochastic events due to the small and spatially simple range of occurrence.

Low Moderate High X Figure 27. Final resiliency condition for the Amicalola Creek population

Figure 28. Predicted areas of urbanization within Amicalola Creek

Etowah River

Urbanization is expected to expand eastward from Dawson and westward from Dahlonega, Georgia towards the upper Etowah River. Northward expansion from Cumming, Georgia along Hwy 19 and Hwy 53 is also expected. In all, this watershed is anticipated to be 20% developed by 2070. As a result from increased levels of urbanization in the status quo scenario, portions to the Etowah River are expected to exhibit characteristics of the urban stream syndrome (flashiness and degraded water quality). Under the Status Quo scenario, we anticipate the range of Bridled Darter within the Etowah River to contract further into upstream reaches that are managed by the U.S. Forest Service. Therefore, as a result of declines in spatial extent this population is expected to have low resiliency to stochastic events.

Low Moderate High X Figure 29. Final resiliency condition for the Etowah River population

Figure 30. Predicted areas of urbanization within the Etowah River

Table 6. Estimated resilience factors and overall resiliency condition for bridled darter populations under the Status Quo scenario

Approximate Occurrence Occurrence Physical Connectivity Water Hydrologic Overall Abundance Extent Complexity Habitat Quality Regime Condition Conasuaga Moderate Low Low Low High Low Moderate Low River Holly Creek Moderate Low Low Low High Low Low Low

Talking Rock 0 0 0 Low High Low Low Extirpated Creek Long Swamp 0 0 0 Low Low Low Low Extirpated Creek Amicalola Moderate Low Low Moderate High Moderate Moderate Low Creek Etowah River Low Low Low Moderate High Moderate Moderate Low

Representation

Representation is expected to decline under the Status Quo scenario. Watershed variability is expected to be reduced by approximately 33%. Because the bridled darter range is expected to contract out of Ridge and Valley and Piedmont provinces into the Blue Ridge, physiographic variability is expected to be reduced by approximately 66% by the year 2070. Under this scenario, behavioral and morphological variation that is currently known in the Etowah and Conasauga rivers will persist. However, resiliency of the populations that represent that variability will be low. Due to degraded habitat and water quality in downstream reaches of occupied rivers, connectivity is unlikely to be restored among populations and continue to limit the exchange of novel and beneficial adaptations and migration to more suitable habitat. This limited representation will reduce the adaptive potential of the Bridled Darter by 2070.

Redundancy

Redundancy for the bridled darter is characterized by having multiple, resilient and representative populations distributed throughout its range. Under the Status Quo scenario, overall redundancy will be reduced by 33% due to the extirpation of two populations. All remaining extant populations are expect to have low resiliency. Under the Status Quo scenario, the bridled darter is expected to have low redundancy. Extant population have experience declines, low numbers, and/or have low spatial complexity.

Connectivity is not expected to improve for the species, range-wide under the Status Quo scenario. Dams have completely isolated the six populations into three groups. As mentioned earlier, the overall lack of connectivity between populations increases the importance of localized stochastic events and the species as a whole is less robust to smaller, more probable, and potentially more frequent stochastic events. Therefore, a key component of resiliency – minimization of the effect of localized extirpation– is not met.

Best Case

In the Best Case scenario we predict wider adoption of conservation measures and policies which involves watershed scale conservation plans (WLFW and watershed HCPs) and enacting a water

policy for Alabama. We still expect rapid urban growth, albeit, at slower rate than under the status quo and worst case scenarios (~100%, Terando et al. pg. 1). Under the Best Case scenario rapidly growing urban areas address environmental concerns and implement water conservation measures and green infrastructure. These actions would lessen the demand on water resources (requiring fewer drinking water supply reservoirs) and minimize urban effects on streams. While large numbers of roads will still be constructed, under the Best Case scenario, road crossings will be constructed that allow for fish passage. In this scenario we expect carbon emissions to peak before 2020 (van Vuuren et al. 2007 pg 132) resulting in a lower probability of extreme weather conditions negatively effecting stream fishes. As a result of a diverse array of conservation actions being undertaken across the landscape, we would anticipate the species to persist or experience a slightly positive response.

Conasauga River

Under the Best Case scenario development proceeds around Dalton, Georgia at a slower rate than under the Status Quo scenario, leading to about 7.6% of the watershed becoming developed. However, urban planners incorporate green infrastructure and manage stormwater. These actions reduce the negative effects development typically has on streams. Much of the river upstream of Dalton, is maintained for agriculture. Conservation programs (Working Lands for Wildlife) have been successfully implemented and because of wide adoption of best management practices (BMPs) by farmers, pollution from herbicide application and poultry litter are reduced. These actions lead to improved water quality in the Conasauga River. These actions increase the potential for the bridled darter to persist in the Conasauga River outside of U.S. Forest Service lands. Range expansion, if it occurs, will be limited due to the legacy effects from current practices. Under the Best Case Scenario, Conasauga River will have a moderate resilience to stochastic events because its range will still be small and simple (confined to the main stem of the Conasauga River).

Low Moderate High X Figure 31. Final resiliency condition for the Conasauga River population

Holly Creek

Urban development is still expected to increase, leading to approximately 4% of this watershed being developed. This lower level of urbanization associated with wider implementation of voluntary conservation measures preserves water quality. Agricultural lands incorporate appropriate BMPs to preserve water quality. Due to the small size and spatial complexity, however, this population will retain a low resiliency to stochastic events.

Low Moderate High X Figure 32. Final resiliency condition for the Holly Creek population

Talking Rock Creek

Under the Best Case scenario, urbanization that is likely to occur in the Talking Rock Creek watershed will not have a negative effect on the bridled darter and improvement in agricultural practices will likely improve the water quality. However, under this scenario translocation of fish into Talking Rock Creek is not assumed. This isolated population with low abundance of bridled darter, while likely to persist, will retain a low resilience to stochastic events.

Low Moderate High X Figure 33. Final resiliency condition for the Talking Rock population

Long Swamp Creek

Like Talking Rock Creek, changes on the landscape are not anticipated to cause significant negative effects to aquatic resources in Long Swamp Creek under this scenario. Bridled darter is anticipated to persist in Long Swamp Creek; however, it is expected to retain a low resiliency because of its current low abundance, small spatial extent, and low spatial complexity is not expected to change even under the Best Case scenario.

Low Moderate High X Figure 34. Final resiliency condition for the Long Swamp Creek population

Amicalola Creek

Urbanization is expected to increase within the watershed; however, its effects will be reduced from conservation measures, green infrastructure, and slower rates of development. Reduced effects of stressors from urbanization and because adjacent lands to Amicalola Creek are owned and managed as a WMA by the State of Georgia will allow this population to persist in all known locations currently occupied and potentially expand to downstream reaches or into previously occupied tributaries. Therefore, it is expected have a moderate resiliency to stochastic events due to an increase in spatial extent occupied.

Low Moderate High X Figure 35. Final resiliency condition for the Amicalola Creek population

Etowah River

Under the Best Case scenario, urbanization is expected to increase by 100% in this watershed. While conservation measures will reduce negative effects to the Etowah River, this rapidly developing area will still see some impacts from increased levels of development and will likely negatively affect bridled dater abundance. Under this scenario, we do not anticipate appreciable declines nor do we expect to see expansion to the range of Bridled Darter within the Etowah River. Therefore, it is expected this population will maintain a low resiliency to stochastic events.

Low Moderate High X Figure 36. Final resiliency condition for the Etowah River population

Table 7. Estimated resilience factors and overall resiliency condition for bridled darter populations under the Best Case scenario

Approximate Occurrence Occurrence Physical Connectivity Water Hydrologic Overall Abundance Extent Complexity Habitat Quality Regime Condition Conasuaga Moderate Moderated Low Moderate Moderate Moderate Moderate Moderate River Holly Creek Moderate Low Low Moderate Moderate Moderate Moderate Low

Talking Rock Low Low Low Moderate Moderate Moderate Moderate Low Creek Long Swamp Low Low Low Low Low Low Low Low Creek Amicalola Moderate Moderate Low Moderate Moderate Moderate Moderate Moderate Creek Etowah River Low Low Low Low Moderate Low Low Low

Representation

Under the Best Case scenrio, all historically occupied physiographic provinces are occupied, albeit with populations that display low to moderate resiliency. Therefore, physiographic province representation is low. Similarly, because all populations exhibit low resiliency, watershed variability is low even though all historically occupied watershed remain occupied. Finally, although populations that exhibit the known genetic, morphological, and behavioral variability will remain extant in this scenario, they do not exhibit high resiliency. Therefore, genetic, morphological, and behavioral representation is considered low.

Redundancy

Redundancy for the bridled darter is characterized by having multiple, resilient and representative populations distributed throughout its range. Under the Best Case scenario three populations of bridled darter will improve to exhibit moderate resiliency and no populations are expected to become extirpated. However, because 50% of the known populations will exhibit low resiliency, the bridled darter is expected to have low redundancy

Connectivity is not expected to improve for the species, range-wide under the Status Quo scenario. Dams have completely isolated the six populations into three groups. As mentioned

67 earlier, the overall lack of connectivity between populations increases the importance of localized stochastic events and the species as a whole is less robust to smaller, more probable, and potentially more frequent stochastic events. Therefore, a key component of resiliency – minimization of the effect of localized extirpation– is not met.

Worst Case

In the Worst Case scenario we anticipate major negative effects in aquatic ecosystems as a result of rapid urbanization (~250% increase in urban areas; Terando 2013, pg. 5). In conjunction with rapid urban growth, we predict that there will be a general lack of conservation measures and policies being implemented at the local, regional, or national levels. Water demand will increase with population and new reservoir construction will take place. In addition to rapid urbanization, carbon emissions are projected to continue to increase above the current levels in this scenario, resulting in a higher probability of extreme weather events that can negatively affect fish species. In areas that remain in agricultural use, there will be an increased amount of herbicide and poultry litter spreading and no protective measures implemented to address water quality issues. Under this scenario, we anticipate a general decline in available suitable habitat, population size, and abundance.

Conasauga River

Under the Worst Case scenario, increased rates of pollutants, nutrients, and endocrine disruptors originating from agricultural practices being discharged into the river will be observed. This increase in the rate of pollutants being input into the river will result in higher concentrations than observed under the Status Quo scenario. Rapid development in downstream reaches will further degrade habitat and water quality. Due to degraded water quality in the Conasauga River adjacent to private lands, we expect the Bridled Darter to be extirpated from these reaches. The bridled darter will likely persist in upper reaches owned and managed by the U.S. Forest Service. However, due to a substantial loss of historical occupied range, we expect to Bridled Dart to have low resiliency in the Conasauga River by the end of 2070.

Low Moderate High X Figure 37. Final resiliency condition for the Conasauga River population

Holly Creek

Under the Worst Case scenario, poultry farming is anticipated to increase within the watershed to match densities in the Sumac Creek watershed immediately adjacent and to the North. Additional poultry houses within Holly Creek will degrade water quality. Water quality degradation will be intensified as other parts of this watershed continue to develop to accommodate larger human

68 populations. Due to the small occupied range, low spatial complexity, and increases in extreme climatic events that are expected to occur under the Worst Case, bridled darter will likely be extirpated from this watershed by 2070 under the Worst Case scenario.

Talking Rock Creek

Given the current low abundance of the population of Bridled Darters in Talking Rock Creek, further habitat degradation from urbanization and increases in extreme climatic events that are expected to occur under the Worst Case scenario will likely cause extirpation of this currently at risk of extirpation population.

Long Swamp Creek

Long Swamp Creek will see substantially more development around the towns of Jasper and Nelson, Georgia. The added pressures of urbanization will continue to degrade water quality and alter flows in this watershed. Mines and agricultural practices that remain will add to degraded water quality. Under the Worst Case scenario, this population that is currently at a high risk of extirpatioin will likely be extirpated by 2070.

Amicalola Creek

Low Moderate High X Figure 38. Final resiliency condition for the Amicalola Creek population

Etowah River

Due to rapid urbanization outward from Atlanta, the Etowah River is anticipated to see a 200% increase in development within the watershed. Declines in physical habitat and water quality, and altered flows are anticipated. Like the Status Quo scenario, we anticipate the range of Bridled Darter within the Etowah River to contract further into upstream reaches that are managed by the U.S. Forest Service. Therefore, as a result of declines in spatial extent, this population is expected to have low resiliency to stochastic events.

Low Moderate High X Figure 39. Final resiliency condition for the Etowah River population

Table 8. Estimated resilience factors and overall resiliency condition for bridled darter populations under the Worst Case scenario

Approximate Occurrence Occurrence Physical Connectivity Water Hydrologic Overall Abundance Extent Complexity Habitat Quality Regime Condition Conasauga Moderate Low Low Moderate Moderate Moderate Moderate Low River Holly Creek 0 0 0 Low Moderate Low Low Extirpated

Talking Rock 0 0 0 Moderate Moderate Moderate Moderate Extirpated Creek Long Swamp 0 0 0 Low Low Low Low Extirpated Creek Amicalola Low Low Low Moderate Moderate Moderate Moderate Low Creek Etowah River Low Low Low Moderate Moderate Low Low Low

Representation

Representation is expected to decline under the Worst Case scenario. Watershed variability is expected to be reduced by approximately 50%. Because the bridled darter range is expected to contract out of Ridge and Valley and Piedmont provinces into the Blue Ridge, physiographic variability is expected to be reduced by approximately 66% by the year 2070. Under this scenario, behavioral and morphological variation that is currently known in the Etowah and Conasauga rivers will persist. However, resiliency of the populations that represent that variability will be low. Due to degraded habitat and water quality in downstream reaches of occupied rivers, connectivity is unlikely to be restored among population. This lost connectivity will continue to limit the exchange of novel and beneficial adaptations and migration to more suitable habitat. This limited representation will reduce the adaptive potential of the Bridled Darter by 2070.

Redundancy

Redundancy for the bridled darter is characterized by having multiple, resilient and representative populations distributed throughout its range. Under the Worst Case scenario, overall redundancy will be reduced by approximately 50% due to the extirpation of three populations. All remaining extant populations are expect to have low resiliency. Under the Status Quo scenario, the bridled darter is expected to have low redundancy. Extant population have experience declines, low numbers, and/or have low spatial complexity.

Summary

Uncertainty

Through the course of this analysis, reasonable assumptions were necessary to assess current and future conditions. These assumptions introduce some uncertainty to our estimates of species viability. Here we identify some key uncertainties within our assessment.

We assumed that historical range is captured by the river length between furthest upstream and furthest downstream records. The actual historical range, prior to European colonization, is unknown (Williams et al. 2007, p. 11). “Its association with slow-flowing habitats suggests that bridled darter could have occurred throughout the Conasauga and Etowah rivers, and possibly in the geographically intermediate Coosawattee River, below the gorge now impounded by Carters Dam and Reservoir” (Williams et al. 2007, p. 11). Therefore, the historical range represented within this assessment may be an underestimate.

As described earlier, abundance was measured qualitatively to avoid directly comparing numeric survey results that utilized disparate methods. This approach was considered appropriate because we were comparing the frequency of “rare” vs. “common” collections and assumed that actual abundance would relate to our qualitative abundance frequency. This method, however, was unable to address actual differences in survey methodology. It is possible abundance may be over or under estimated. For example, because catch per unit effort was rarely recorded high or low bridled darter counts per record could incorrectly represent actual abundance within a population.

Physical habitat was partly assessed based on the amount of natural vegetation within the Active River Area (ARA) of an entire occupied HUC10 watershed (population). In all populations, much of the headwaters are in forested land and are not occupied by bridled dater. This metric likely over estimates the amount of natural riparian vegetation and in the future a more appropriate method may be to consider only stream reaches that are occupied by the species of interest for this analysis.

Future Viability

The future scenario assessment has sought to understand how viability of the bridled darter may change over the course of 50 years in the terms of resiliency, representation, and redundancy. To account for considerable uncertainty associated with future projections, we defined three scenarios that would capture the breadth of changes likely to be observed in the upper Coosa River basin to which the bridled darter will be exposed. These scenarios considered two primary elements of change: urbanization (Terando et al. 2014) and climate change (IPCC 2013). While we consider these scenarios plausible, we acknowledge that each scenario has a different probability of materializing at different time steps. To account for this difference in probability, a

73 discretized range of probabilities was used to describe the likelihood a scenario will occur based on professional judgment (Tables 9 and 10).

Table 9. Explanation of confidence terminologies used to estimate the likelihood of a scenario (after IPCC guidance, Mastrandrea et al. 2011)]

Confidence Terminology Explanation Very likely Greater than 90% certain Likely 70-90% certain As likely as not 40-70% certain Unlikely 10-40% certain Very unlikely Less than 10% certain

Table 10. Likelihood of a scenario occurring at 10 and 50 years.

Status Quo Best Case Worst Case 10 years Very likely Unlikely As likely as not 50 years Likely Unlikely As likely as not

In the Status Quo scenario two extant populations of bridled darter are expected to become extirpated. This will decrease overall redundancy for the species as well as representation (the Coosawattee River will no longer be represented with the extirpation of the Talking Rock Creek population). Physiographic representation will decline in the future because the bridled darter’s range is expected to contract out of the Piedmont and Ridge and Valley to upstream stream reaches that are owned and managed by state and federal agencies within the Blue Ridge physiographic province. This scenario is very likely and likely within 10 and 50 years, respectively (Table 4).

The Best Case scenario assumed slightly slower rates of development and wider implementation of conservation activities that reduced the impact of development on streams. Additionally, this scenario assumed that through broad climate policies greenhouse gas emissions would begin to peak and decline, decreasing the likelihood of pervasive extreme climate events. Under this scenario, all extant populations of bridled darter would persist. Due to continued urban growth and delayed response from conservation actions being implemented, we considered range expansions to be unlikely even under this scenario. As a result, the bridled darter is expected to slightly benefit under the Best Case scenario due to increased resiliency of some populations. This scenario is considered unlikely to occur in both 10 and 50 year projections because it is unlikely that the broad conservation actions and policies will be implemented that require this scenario to play out.

In the Worst Case scenario urban growth proceeds more quickly than current rates, conservation actions are not implemented widely, and the likelihood of extreme climate events increase as

greenhouse gas emissions continue to increase. As a result, three populations become extirpated and three remain extant. The populations that remain decline in resiliency due to range contractions out of privately held land and into publicly held lands in the Blue Ridge and are exposed to extreme climate events. Like the Status Quo scenario, the Worst Case scenario sees an overall decrease in redundancy and representation. This scenario has is “as likely as not” to occur within 10 years and “likely” to occur within 50 years.

Overall Summary

Currently, the bridled darter continues to occupy all streams where it was known to occur historically. Based on collection records from the last 10 years, five populations occur over shorter overall stream lengths than historical records, suggesting range reduction in these five populations. No population of bridled darter currently exhibits high resiliency due to the reduction in extent of occupied habitat, low abundance of individuals per collection record, a linear simple, arrangement of records, as well as stressors affecting habitat and water quality. Similarly, representation and redundancy is currently low for this species because multiple resilient populations are lacking, connectivity is limited among populations, and this species is increasingly becoming isolated to the upstream limits of its range in the Blue Ridge physiographic province.

Our future scenarios assessment considered the current viability of the species to project likely future viability given plausible scenarios of urban development and climate change. Only in the Best Case scenario did the species persist in all known populations. However, under this scenario bridled darters were not expected to expand outside of historical range boundaries and resiliency was expected to be moderate at best. Two and three populations were extirpated under the Status Quo and Worst Case scenarios, respectively. Resiliency, representation, and redundancy declined in both these scenario due to further range contractions and increased likelihoods for extreme climatic events to impact populations.

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