Species Status Assessment Report for the Barrens Darter (Etheostoma Forbesi)

Species Status Assessment Report for the Barrens Darter (Etheostoma forbesi)

Version 2.0

Acknowledgements: This Species Status Assessment would not have been possible without the research and assistance of Dr. Richard Harrington, Yale University Department of Ecology and Evolutionary Biology, Dr. Hayden Mattingly and his students, Tennessee Tech University School of Environmental Studies, Dr. John Johansen, Austin Peay State University Department of Biology, and Mark Thurman, Tennessee Wildlife Resources Agency.

TABLE OF CONTENTS Chapter 1: Introduction ...... 3 Chapter 2: Biology and Life History ...... 4 Taxonomy ...... 4 Genetic Diversity ...... 5 Morphological Description ...... 5 Habitat ...... 6 Lifecycle ...... 7 Population Needs ...... 9 Species Needs ...... 9 Historic Range and Distribution ...... 10 Chapter 3: Factors Influencing Viability ...... 11 Landuse and Associated Impacts ...... 11 Predation and Competition ...... 15 Climate Events ...... 16 Demographic Effects ...... 17 Conservation Actions ...... 18 Chapter 4: Current Management Unit Condition and Species Viability ...... 18 Population Elements ...... 18 Habitat Elements...... 19 Current Management Units and Population Status...... 20 Current Species Level Status ...... 25 Chapter 5: Future Conditions ...... 25 Scenario 1 ...... 27 Scenario 2 ...... 31 Scenario 3 ...... 34 Status Summary ...... 38 Overall Summary ...... 40 References ...... 41

Chapter 1: Introduction The Barrens Darter (Etheostoma forbesi Page and Ceas 1992) is a small fish endemic (restricted to a locality or region) to streams in the Collins River watershed on the Barrens Plateau in middle Tennessee. The Barrens Darter was designated a Category 2 Candidate species in 1994 (59 FR 58982), and remained such until that list was discontinued in 1996 (61 FR 64481). A species assessment and listing priority form was completed for the Barrens Darter in 2006, but due to the limited amount of data available on the species at the time, it was not determined to be a candidate for listing at the time (USFWS 2006). The Barrens Darter was petitioned to be listed under the Endangered Species Act of 1973, as amended (Act), by the Center for Biological Diversity as part of the 2010 Petition to List 404 Aquatic, Riparian and Wetland Species from the Southeastern United States (CBD 2010, p. 432-433). This SSA Report for the Barrens Darter provides the biological support for the decision on whether or not to propose to list the species as threatened or endangered and, if so, where to propose designating critical habitat. Importantly, the SSA Report is not the decision by the Service on whether this species should be proposed for listing as a threatened or endangered species under the Act. Instead, this SSA Report provides a review of the available information strictly related to the biological status of the Barrens 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 decision 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 Barrens Darter to sustain natural populations in its native range 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 (Shaffer and Stein, 2000, entire; Wolf et al. 2015, entire).

• Resiliency describes the ability of populations to withstand stochastic events (arising from random factors). We can measure resilience based on metrics of population health; for example, birth versus death rates and population size. 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 species’ geographical range and other factors as appropriate.

• Redundancy describes the ability of a species to withstand catastrophic events. Measured by the number of populations, their resilience, and their distribution (and connectivity), Figure 1-1 Species Status Assessment redundancy gauges the probability that the Framework 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 Barrens Darter, both currently and into the future, we assessed a range of conditions to allow us to consider the species’ resilience, 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. The format for this SSA Report includes: (1) the resource needs of individuals and populations (Chapter 2); (2) the Barrens Darter’s historical distribution and a framework for determining the distribution of resilient populations across its range for species viability (Chapter 3); (3) the likely causes of the current and future status of the species and determining which of these risk factors affect the species’ viability and to what degree (Chapter 4); and (4) a description of the viability in terms of resilience, redundancy, and representation (Chapter 5). 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 Barrens Darter.

Chapter 2: Biology and Life History Taxonomy The Barrens Darter was first described from Duke Creek (Figure 2-4) as Etheostoma forbesi by Page and Ceas in a larger review of the E. squamiceps (Spottail Darter) species complex that described five new species (Page et al. 1992, pp.633-634). Previous collections had be assigned to Spottail Darter, Dirty Darter, E. olivaceum, or Fringed Darter, E. crossopterum (Page et al. 1992, p.633). Near and Keck formally defined the Spottail Darter complex as the clade Stigmacerca in the subgenus Catonotus, the egg clustering darters (Near et al. 2011, p.595). This is a very diverse group of darters and includes the only species in the perch family (Percidae)

known to produce sounds (Johnston and Johnson 2000, p.475). The Catonotus darters are also notable for the level of parental care the male provides by guarding the eggs (Etnier and Starnes 1993, pp.449-450). Also within the Stigmacerca clade is the Fringed Darter, Etheostoma crossopterum, which is slightly larger than the Barrens Darter and is found in tributaries of the lower ends of Tennessee and Cumberland River systems. This species occurs as a disjunct population in the Barren Fork, primarily downstream from stream reaches where the Barrens Darter historically occurred. Genetic Diversity Endemic to headwater streams in the Collins River system, the Barrens Darter has a naturally narrow distribution. There have been no published population genetic studies on this species; however analysis of the mitochondrial gene, cytochrome b (cyt b), shows only a single common haplotype (set of genes inherited together) found in all populations across its range, with very few individuals bearing cyt b haplotypes that differ from this common one by one or two mutations (Richard Harrington, pers. comm.). Analyses of molecular variation of Barrens Darter cyt b haplotypes show no significant correlation of this limited genetic diversity with geographic distribution. Preliminary analysis of the nuclear gene S7, shows a similar pattern, with two common haplotypes distributed throughout the Barrens Darter range and no support for geographic structuring of the genetic variation. Ongoing work using a genomic sequencing technique (RADseq) may provide increased resolution. Given the limited geographic range of this species, this low level of genetic diversity is not unexpected, but may also point to adequate connectivity between watersheds. Genetic analysis has also shown evidence of potential hybridization between Barrens Darters and Fringed Darters. A small number of specimens collected in Hickory Creek (Figure 2-4) that were initially identified morphologically as Fringed Darters were found to have Barrens Darter mitochondrial haplotypes. Preliminary nuclear genome analysis of these specimens showed that the nuclear genes matched Fringed Darters. Since the mitochondrial genome is maternally inherited, the data available at this time may indicate unidirectional hybridization. Without a larger sample size of nuclear data, it is not possible to tell whether this mitochondrial introgression happened recently or longer ago (Richard Harrington, pers. comm.). Morphological Description The Barrens Darter is a small, drab-colored, benthic darter, with an observed maximum length of 97 millimeters (mm) (3.8 inches (in)) (Hansen et al., 2006). As is typical of the subgenus Catonotus, Barrens Darters are laterally compressed (taller than wide), have rounded caudal (tail) fins, and, denoting their placement in the clade Stigmacerca, they have three dark spots in a vertical line on the base of the tail (Page et al. 1992, p.623). Barrens Darters are tan overall with brown mottling. Nuptial males, which are larger than females, become much darker with swelling developing in the head and nape region. The fins become mostly black, and the second dorsal fin shows 4-5 distinctive clear or yellow bars and a yellow-gold margin. The Fringed Darter is very similar in appearance to the Barrens Darter and occurs in some of the same stream systems, making identifications in the field problematic. Nuptial males are distinguishable by the pattern on the second dorsal fin, with Fringed Darters having 6-7 rows of clear or light yellow crescents and a white margin compared to the Barrens Darter described

above. The third branch of the dorsal fin rays are greatly elongated in male Fringed Darters, but roughly equal with the other branches in the Barrens Darter. Females and juveniles of the two species are distinguishable meristically (using scale and fin ray counts) within the Caney Fork drainage as given by the counts in Table 2-1. The Barrens Darter also co-occurs with a third species of Catonotus, the Fantail Darter (Etheostoma flabellare), in Charles Creek, but the two species are distinguishable by the three spots on the base of the tail fin in Barrens Darters (Layman et al. 1993, p.68).

Table 2-1. Counts of second dorsal fin rays in Barrens Darter and Fringed Darter. Putative Fringed Darter from McMahan Creek and Barrens Darter from Scott Creek included. (Table provided by Rich Harrington, from meristic data collected by Tom Near). Habitat Barrens Darters inhabit small headwater streams with slab rock cobble substrates and strong groundwater influence (Figure 2-1). In a habitat association study, Zuber (2014, pp. 36-51) found Barrens Darters only in streams with a link magnitude of 5 or less. From a point in a stream, link magnitude is the number of unbranched source streams located upstream. Thus, a low link magnitude measure, such as 5 or less, indicates the Barrens Darter’s affinity for small streams and headwater habitats. Barrens Darters were also found to have an association with lower than average dissolved oxygen levels, which may be an indication of groundwater influence. As a headwater specialist species, tolerance of lower than average oxygen levels would be advantageous because headwaters are likely to become intermittent, with only stagnant pools available during the warmest periods of the year and during periods of drought. In times of drought, if the discharge of groundwater is severely reduced, Barrens Darters may move downstream into more permanent water if suitable habitat is available. No correlation was found with microhabitat variables outside of the spawning season (Zuber 2014, p. 46). During the spawning season, Barrens Darters congregate in shallow riffle and run areas with roughly 4- to 12-in slab rock cobble with cavities underneath. Barrens Darters, in comparison to Fringed Darters, have been observed using smaller nest rocks in shallower water (Bergen 2012, p. 436).

This difference could be due to what was available where the observations occurred rather than a true difference of nest rock size and depth preference.

Figure 2-1. Barrens Darter Habitat. Left: Charles Creek, illustrating the slab rock cobble. Right: McMahan Creek, a stream with strong groundwater influence.

Lifecycle The lifecycle of the Barrens Darter (Figure 2-2) and other members of its subgenus, Catatnotus, includes a unique reproductive strategy. Catonotus darters are cavity nesting egg clusterers that exhibit parental care. Life stage needs (Table 2-2) include nest guarding, whereby the male establishes a territory around a cavity under a flat rock and, based on its body size and quality of its nest cavity, attracts females. The males will also produce knocks, drums and purrs to court females as well as to defend the nest cavity from other males (Johnston and Johnson 2000, p.477). Once a female has chosen to spawn with a male, the pair will invert under the rock and the female will adhere eggs to underside of the rock in a single layer. Multiple females will lay eggs in a single in a single nest, and there may be over 900 in a nest. The male will clean the eggs and guard them from predators until they hatch in 5 - 11 days (Page 1974). Nesting occurs from mid-March to early June (Bergen et al 2012, p. 435)

Barrens Darter larvae are non-pelagic and stay near the substrate. The species matures in one to two years, though males may not breed until their second year due to female preferential selection of bigger males and the competition for nest cavities. Barrens Darters have a roughly three year lifespan and may rarely live to age four (Hansen 2006, pp. 65, 67). Prey items likely include midge, mayfly, and caddisfly larvae as well as microcrustaceans, similar to the known prey items consumed by Fringed Darters (Page 1974, entire).

Figure 2-2. Barrens Darter Lifecycle

Life stage Needs Sources Egg • Male Guarding Page 1974, entire • 60-75℉ Page 1980, entire Larvae • Clean Gravel Page 1974, entire substrate Page 1980, entire Juveniles • Gravel or other Page 1974, entire suitable cover Page 1980, entire • Small aquatic arthropods for food • Appropriate water quality Adult • Clean water quality Page 1974, entire • Available cover Page 1980, entire • Stable hydrograph Hansen 2006, entire • Aquatic arthropods Bergen 2012, entire for food Zuber 2012, entire • Clean slab rock cobble for spawning habitat Table 2-2. Barrens Darter life stage needs

Population Needs Each Barrens Darter population needs to be able to withstand, or be resilient to, stochastic events or disturbances. Although they are infrequent, stochastic events are reasonably likely to occur and they can drastically alter the ecosystem where they happen. Classic examples of stochastic events include drought, major storms (hurricanes), fire, and landslides (Chapin et al. 2002, pp. 285-288). To be resilient to stochastic events, populations of Barrens Darter need to have an abundance of several hundred individuals and occupy multiple sites in multiple watersheds (spatial extent). Additionally, populations need to exist in locations where environmental conditions provide suitable habitat and water quality such that adequate numbers of individuals can be supported. Without all of these factors, a population has an increased likelihood for localized extirpation. Species Needs For a species to persist and thrive over time, it must exhibit attributes across its range that relate to either representation or redundancy (Figure 2-3). 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 Barrens Darter to exhibit adequate representation, resilient populations should occur in the ecoregion to which it is native (Eastern Highland Rim); these populations should occur at the widest extent possible across the historic range of the species; and they should occupy multiple tributaries in drainages where they are native. The breadth of morphological, genetic, and behavioral variation should be preserved to maintain the adaptive capacity of the species. Finally, natural levels of connectivity should be maintained between representative populations because it allows for the exchange of novel and beneficial adaptations where connectivity. Situations where connectivity is naturally lower and the species is more isolated can function as a mechanism for localized adaption and variation.

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 Barrens Darter is characterized by having resilience in multiple streams across the native range of the species. In terms of redundancy connectivity is important, because it allows for immigration and emigration and increases the likelihood of recolonization should a population become extirpated.

Figure 2-3. How resiliency, representation, and redundancy are related to species viability Historic Range and Distribution The Barrens Darter is a highly endemic species with a very narrow distribution in Middle Tennessee in the headwaters of the Collins River, which is a tributary of the Caney Fork River in the Cumberland River Drainage. The range of this species lies in portions of Coffee, Cannon, Warren, and Grundy Counties. This species is limited to the headwaters of the Barren Fork and Collins Rivers and the upper portions of Charles Creek, a direct tributary to the Collins River. At the time of description, this species was known from six subwatersheds (Figure 2-4). Each of these subwatersheds acts as a separate management unit (MU), where the change within the unit is likely to outpace significant movement of Barrens Darters between the units (Mattingly and Johansen, 2017 interim report, p.2; Hayden Mattingly and Rich Harrington, pers. comm.). Barrens Darters were found in a seventh subwatershed in the headwaters of the Collins River during the preparation of this report which validates the record of a single Barrens Darter taken from Scott Creek in Grundy County during 2003 (Rich Harrington, pers. comm.).

Figure 2-4. Management units across the range of the Barrens Darter. Blue ellipses represent currently occupied units while yellow ellipses represent extirpated units. Current Range Based on museum collection records from Fishnet2.net and surveys compiled by Rich Harrington (pers. comm.), surveys carried out as part of studies at Tennessee Tech University (Zuber 2013, Bergen et al. 2012, Hansen et al. 2006), and an ongoing survey by Hayden Mattingly and John Johansen (TTU and Austen Peay State University, respectively) the Barrens Darter is found in five of the seven units where it has been found historically. Barrens Darters have not been collected in the West Fork Hickory Creek system (Unit 6) since the early 1980s and appear to have been replaced by Fringed Darters (Figure 2-4). Barrens Darters have also not been seen in the tributaries to the North Prong of the Barren Fork (Unit 2) since at least 2001. Chapter 3: Factors Influencing Viability Landuse and Associated Impacts Land cover and land use have a strong influence on the quality and quantity of water in streams (Allan 2004, entire). Vegetation type can affect the timing, amount, and quality of water in streams. Livestock can have direct and indirect effects on water quality through waste and sedimentation. The Barrens Plateau area of Tennessee is very susceptible to impacts from

agriculture according to the Tennessee State Wildlife Action Plan (TN SWAP 2015, ch. 4 p. 23) (Figure 3-1). Human development can also have significant impacts to stream systems in quality and quantity (Freeman and Marcinek 2006, entire).

Figure 3-1. Potential agricultural impacts to priority aquatic habitats in the Barrens Plateau area from the TN SWAP analysis for the state (TN SWAP, ch. 4, p. 23). The Barrens Plateau area shows up as one of the areas with the highest risk in the state. Pasture and Livestock Many of the springs and streams within the Barrens Darter’s range are used as water sources for cattle and other livestock (Figure 3-1). Cattle access is known to increase bank erosion, increasing turbidity and sedimentation in the springs. Darters require clear water for their spawning displays to be successful and clean vegetation for egg laying. Sedimentation from livestock also has the potential to cover cobble and other structure, resulting in lower habitat quality, fewer food items, and limited spawning cavities. The increased turbidity and reduced riparian vegetation leads to increased water temperatures that reduce dissolved oxygen levels and can stress darters (Allan 2004, p. 262). Influxes of large amounts of animal waste increases the amount of nutrients in the water and further reduces visibility, which can impact the spawning displays of Barrens Darters. Higher nutrients lead to higher biological oxygen demand and reduce the dissolved oxygen levels in the water. Increased bacterial levels may also reduce egg viability and increase the risk of infection (Pat Rakes, pers. comm.). Fungus-covered eggs in Barrens Darter nests have been observed in Lewis Creek (Unit 3) and Duke Creek (Unit 4) (Hansen et al. 2006, p.66; Bergen et al. 2012, p.438). Parts of the West Fork Hickory Creek watershed (Unit 6) have been listed as impaired or threatened waters (303d) due to livestock grazing and animal feeding operations contributing to altered riparian (streamside) vegetation, increases in nitrogen containing compounds (nutrients), and increased levels of the bacteria

Escherichia coli (E. coli) which is associated with animal waste (TDEC 2018 draft list of impaired and threatened waterways). An activity often associated with livestock operations is the clearing of vegetation up to the edge of the springs and runs that the Barrens Darters rely on. Trees and shrubs are cleared to allow easier access for cattle or to provide views of the stream. Riparian vegetation acts to stabilize banks and reduce overland runoff, so when it is removed, sedimentation increases (Barling and Moore 1994, p. 544; Beeson and Doyle 1995, p. 989). Removal of riparian vegetation can also lead to an increase in water temperature because the stream is no longer shaded (Brazier and Brown 1973, p. 4; Barton et al. 1985, p. 373; Pusey and Arthington 2003, p. 4).

Figure 3-1. Pigs in Cooper Branch, a tributary to Duke Creek, and just upstream of a Barrens Darter collection site. Nurseries Plant nurseries and sod farms are common within the range of the Barrens Darter. McMinnville, Tennessee proclaims itself as “The Nursery Capital of the World” and claims 400 nurseries in Warren County alone (City of McMinnville, http://www.mcminnvilletenn.com/city_government/index.php). There are more than 200 nurseries and greenhouses registered in the three counties occupied by the Barrens Darter, but

this may not represent the total number (Tennessee Department of Agriculture, https://agriculture.tn.gov/listplant.asp). Many of these nurseries produce perennial crops such as trees and shrubs that can increase the amount of evapotranspiration (water used by plants) for an area, reducing groundwater recharge and baseflow in the streams and springs that the Barrens Darter relies on (Allan 2006, p. 264- 266). Many of the nurseries also heavily irrigate the plants they are growing. The water for irrigation is drawn from both wells and surface water in this area. Extensive irrigation can directly and indirectly reduce stream flow, leading to increased water temperatures and reduced habitat (Siebert et al. 2010, pp. 1863-1864; Sophocleous 2002, pp. 93-112). Another concern regarding nurseries is the use of pesticides and fertilizers. Pesticides and fungicides are used on ornamental plants to reduce disease and maintain attractive plants for sale, often at higher levels than used on food or animal feed crops. Some of these common pesticides and fungicides have been shown to cause oxidative stress and reduced brain chemical activity in darters in agricultural and urban streams (Diamond et al. 2016, entire). Fertilizer runoff increases available nutrients in streams, resulting in higher biological oxygen demand and other impacts discussed above in the Livestock section. At higher concentrations, common fertilizers can be directly toxic to fishes. One landowner on Liberty Creek reported that there had been a fertilizer spill that resulted in a fish kill in that creek between 15-20 years ago (John Johansen and Jacob Hartman, pers. comm.). Row Crops Row crops are common within the Barrens Darter’s range. Corn and soybeans are the predominant crops planted in this area, some of which are irrigated. Row crops contribute to many of the same stressors mentioned under the Nurseries section as well as sediment runoff from tilled fields. Row crops cover a larger land area than the nurseries, but may not have as concentrated effects. 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 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. 179). Streams affected by urbanization have been described to exhibit an “urban stream syndrome” (Matthaei and Lang 2016, p. 180; Wenger et al. 2009, p. 1090; Walsh et al. 2005, p. 707). The “urban stream syndrome” consistently manifests as more variable stream flows, higher amounts of pollutants, altered channel stability and morphology, and may include reduced baseflow and increased suspended solids. Also found in urban streams is a reduced number of total aquatic species with an increase in tolerant species. (Walsh et al. 2005, p. 712; Paul and Meyer 2001, p. 349). The storm discharge of urban streams can be twice that of rural streams draining a watershed of similar size (Pizzuto et al. 2000, p. 81, Rose and Peters 2000, p. 1454), and the frequency of channel forming events can be ten times that of pre-development conditions (Booth and Jackson 1997, p. 1078). Therefore, urbanization is anticipated to increase the magnitude of nearly all stressors described above. While the range of the Barrens Darter is mostly rural agricultural land, the towns of Centertown and Morrison, TN are in watersheds where Barrens Darters are native as well as several other unincorporated

communities such as Summitville and Woodland. Tennessee State Highway 53 also runs across the headwaters of all of the Barrens Darter management units increasing the chances of development in the headwaters and the opportunity for various contaminants to make their way into the streams either through spills or runoff. Predation and Competition Native Predators Various centrarchid (sunfish) species such as Green Sunfish (Lepomis cyanellus) are found in the same habitats as Barrens Darters (Rakes 1989, p. 48). These fishes are predatory and are known to occasionally prey on Barrens Darters. A variety of riparian predators (kingfishers, herons, watersnakes, etc.) also likely prey on darters. In sufficient habitat and with healthy population numbers, it is unlikely that predation poses a threat population persistence (resilience). Competition and Hybridization In the West Fork Hickory Creek watershed (Unit 6) and Mud Creek in the South Prong Barrens Fork Watershed (Unit 5), Barrens Darters have been replaced by their larger relative, the Fringed Darter (Figure 3-2). Mitochondrial genetic analysis of Fringed Darters collected in West Fork Hickory Creek has revealed some individuals with hybrid ancestry with Barrens Darters. The analyses completed so far are not able to determine how recently this hybridization may have occurred. Data collected so far would support a hypothesis of uni-directional gene flow from Barrens Darter into Fringed Darter populations, and possible bias of female Barrens Darters hybridizing with male Fringed Darters and not vice versa. This may point to female Barrens Darters preferentially selecting larger male Fringed Darters to breed with when both species co- occur or there is competition for spawning cavities. Although one study indicated Barrens Darters were using smaller rocks for spawning in shallower water than has been observed for Fringed Darters (Bergen et al. 2012, p.436), there have been no analyses of spawning habitat associations where the two species are syntopic (co-occurring in the same reach of stream). Additionally, the use of smaller rocks in shallower depths by Barrens Darters may have been an artifact of what habitat was available at the sample sites (Hayden Mattingly, pers. comm.).

It is not clear whether the encroachment of Fringed Darters into the range of Barrens Darters is due to direct competition, changing conditions, or the filling of a vacant niche after Barrens Darters had been eliminated from an area. As riparian vegetation is cleared, sediment loads increase, and water temperatures warm, conditions in headwaters become more like those in larger streams. This shift makes the habitat more favorable for fish in mid to large sized streams and creates a phenomenon known as native invasion (Scott and Helfman 2001, pp.9-11). In this case, the Fringed Darters could gain a competitive advantage over the Barrens Darters that had been dominant in a portion of a stream. Fringed Darters and Barrens Darters have not been collected together, though genetic data indicates that they have co-occurred and interbred at some point in West Fork Hickory Creek. It is also possible that Fringed Darters are filling a vacant niche after a different stressor eliminated Barrens Darters.

Figure 3-2. Collections of Barrens Darters and Fringed Darters across time, including negative records for either species. Data from verified museum specimens and TTU field surveys. Maps courtesy of Rich Harrington. Climate Events Droughts reduce stream discharge which leads to a reduction of available habitat, and if shallow areas dry out and strand fish in isolated pools, the fish become easier targets for predators. In conjunction with livestock access, drought-reduced stream discharge can result in a very high concentration of animal waste in streams inhabited by Barrens Darters. Portions of many of the streams in the Barrens area are intermittent during drier months, and drought increases the amount of stream that is dry. During drought, fish may able to move downstream to more permanent water, or, if extirpated at a site, darters could recolonize the dried stretches of stream from drought refugia. On the other extreme, heavy rains can increase the amount of sediment washed into as stream. High flows through a stream also contributes to streambed erosion, downcutting and bank incision, as well as substrate instability (Figure 3-3). All of these symptoms reduce the quality of habitat in the stream for Barrens Darters. Human development and the increase in impervious surfaces associated it, exacerbates these effects by increasing the flashiness of stream discharge (Booth and Jackson 1997, p. 1078).

Figure 3-3. Charles Creek, illustrating the bank incision and streambed erosion associated with an altered hydrograph.

In the Southeast, clear trends in climate predictions are limited. Variability in weather is predicted to increase, resulting in more frequent and more extreme dry years and wet years over the next century, though increases in variability are already occurring (Mulholland et al. 1997, entire, Ingram et al. 2013, entire). Average and extreme temperatures are also expected to increase over time. More droughts will increase the likelihood that Barrens Darter streams are impacted by reduced discharge, resulting in the reduction of populations. Droughts will also increase the reliance on groundwater for irrigation of crops in the Barrens region and may force municipalities to use secondary water sources, which has the potential to reduce discharge further. More extreme wet weather events will result in more flooding which will further alter habitat. Warming temperatures overall would contribute to warming waters and reduced dissolved oxygen. Demographic Effects Species restricted in range and population size are more likely to suffer loss of genetic diversity due to genetic drift, potentially increasing their susceptibility to inbreeding depression, decreasing their ability to adapt to environmental changes, and reducing the fitness of individuals (Soule 1980, pp.157-158; Hunter 2002, pp. 97-101; Allendorf and Luikart 2007, pp.117-146).

Conservation Actions Outside of a few surveys and life history studies, there have not been any targeted conservation efforts for the Barrens Darter. This species occurs entirely on private land and thereby does not receive the benefits of conservation land. Efforts have been made to fence livestock out of streams and provide them alternate water sources in some places where Barrens Darters occur. These are very limited in scale and amount of overlap with the Barrens Darter range. Most of these efforts have been funded and organized through Partners for Fish and Wildlife agreements with landowners, but most of the agreements have expired, so it is unclear whether riparian buffer maintenance is continuing at sites where the agreements were applied. Chapter 4: Current Management Unit Condition and Species Viability Current habitat and population conditions are described below. This section details specific stressors acting within the occupied watershed. Additionally, collection history and qualitative abundance data are provided. Current population resilience is assessed for each location and Management Unit specifically, followed by a summary of range-wide redundancy and representation. To qualitatively assess current viability we considered 6 components (Table 4-1) that broadly relate to either characteristics about the population specifically (“Population Elements”) or the physical environment (“Habitat Elements”). Population Elements evaluated were approximate abundance, age structure, and occurrence extent. Habitat Elements evaluated were habitat quality, water quality, presence of Fringed Darters, and occurrence complexity. For our analysis we divide the species range into 6 Management Units (MUs) based on the separate watersheds where the species occurs (Figure 2-4) (Mattingly and Johansen 2017, pp. 2- 3). Dispersal of Barrens Darters between Management Units 2, 3, 4, and 5 via the larger streams that connect them (Figure 2-4) is likely infrequent, owing to the species’ strong affinity for headwaters (Bergen et al. 2012, p. 438; Zuber 2014, pp. 38, 46) Population Elements To evaluate population elements, we pulled data from ongoing surveys for the Barrens Darter (Mattingly and Johansen 2017, and updates, entire; Rich Harrington, pers. comm.) as well as other records from the past 10 years (Zuber 2014, entire). The ongoing survey is being conducted first at sites where Barrens Darters were collected in Zuber’s survey and then expanding to other historic sites and other likely localities. These survey efforts are standardized and use methods to specifically target darters across all size classes. Due to population variability through time and across sites, as well as differential collection techniques between surveys, approximate abundance was characterized as “low,” “medium,” or “high” based on the average number of Barrens Darters collected at all the sites in a management unit in the period 2009 – 2017 (Table 4-2). Population complexity was measured based on the number of age classes present and whether juveniles were collected in the most recent survey. Age classes were divided into <50 mm, 50-68 mm and >68 mm based on the length-frequency diagram from the ongoing survey (Mattingly and Johansen 2017, p.6).

Occurrence extent was measured as the proportion of a MU occupied by Barrens Darters within the last 10 years as compared to the maximum extent. Museum and survey data was used to classify this metric. Habitat Elements Physical Habitat was determined using the Tennessee Department of Environment and Conservation (TDEC) stream habitat assessment protocol for moderate to high gradient streams (TDEC 2017, p. I.I-D-1-24) that was carried out as part of the survey by Mattingly and Johansen (2017, entire). This protocol scores habitat quality based on metrics such as sediment deposition, substrate availability, riparian vegetation, etc. Scores were broken out with Poor and Marginal classifications (scores <100) counting as “low,” Suboptimal (scores 101-150) as “moderate,” and Optimal (scores 151-200) classified as “high.” Site scores were averaged across the MUs. Water quality is based on designations from the US Environmental Protection Agency (EPA) and TDEC, such as impaired and threatened waters lists (covered by section 303(d) of the Clean Water Act) as well as observations from field surveys. Presence of Fringed Darters is a metric of change that has occurred within MUs, since they were not known from the upper ends of the watersheds during early surveys in the area (Figure 3-2), and may either compete, hybridize with, or replace Barrens Darters. Classifications were based on whether Fringed Darters were present in a watershed with Barrens Darter, occurring at the same site, or replacing Barrens Darters. Data is based on museum and survey records. Occurrence complexity is based on presence of records of Barrens Darters in tributaries in addition to the mainstem of a MU. Distribution across a more complex stream network increases resilience in a MU, reducing the likelihood that the Barrens Darters will be extirpated by a catastrophic event such as a chemical spill or the construction of a feedlot or other stressor upstream.

Quality High Moderate Low Unsuitable Physical 151-200 101-150 0-100 Unable to Habitat support survival (TDEC scores) Water Quality Minimal or no Issues Issues known to Unable to known water recognized (e.g., impact support survival quality issues 303(d) streams) populations 2-3 age classes Population One age class; One age class, present; Extirpated Complexity juveniles present no juveniles juveniles present Approximate Collections of Collections of Collections of Abundance between 15 and None observed >15 individuals <5 individuals (per 100m) 5 individuals Occurrence Entire known <30% decline >30% decline in Extirpated Extent range currently from known known range occupied range Presence of Not sympatric in Sympatric but Sympatric and Extirpated Fringed unit not syntopic in syntopic in MU Darters unit or replaced Occurrence Occupies main Occupies main Occupies main Extirpated Complexity channel and channel and one channel multiple tributary tributaries Table 4-1. Definitions of conditions for components used to assess current conditions for the Barrens Darter. Current Management Units and Population Status For Barrens Darters to exhibit high representation, they must be exist across their native range in resilient MUs. Within each MU, Barrens Darters should occur in healthy numbers throughout a large portion of the stream that was historically occupied. Loss of any extant MU compounds the already hindered representation of the species caused by the extirpation of MUs 2 and 6. High redundancy for the Barrens Darter is characterized by having multiple resilient and representative populations distributed within the species’ ecological setting and across its range. Increased connectivity would further improve redundancy by reinforcing existing populations and increase the likelihood for reestablishment of lost populations. MU 1: Charles Creek Charles Creek is separated from the rest of the MUs by being a direct tributary to the Collins River rather than flowing into the Barrens River. The lower end of Charles Creek flows through the city of McMinnville, TN. All records for Barrens Darters within Charles Creek have been in the upper third of its watershed. Over the course of the past 24 years, there appears to have been a decline in the numbers of Barrens Darters collected despite improvements in detection methods

through quantitative kick seining (Zuber 2014, p. 28; Mattingly and Johansen 2017, p. 5, Hayden Mattingly, pers. comm.). The predominant land use in the Charles Creek watershed is pasture and row crops. In addition, several plant nurseries are present. Charles Creek suffers from a flashy hydrograph that has impacted the substrate and other habitat features. Threats occurring in this MU include altered hydrology resulting in scour during flooding, very limited riparian vegetation, and livestock activity. Much of the streambed has been eroded to bedrock, limiting cover and sheltering habitat. Fringed Darters have been collected in the lower reaches of Charles Creek within recent years. In Charles Creek, habitat elements are generally moderate, but population elements are in low condition, especially approximate abundance. Therefore, current resiliency in the Charles Creek MU is low (Table 4-2). MU 2: North Prong Barren Fork Management Unit 2 consists of the North Prong of the Barren Fork River and its tributaries, as well as a couple of direct tributaries to the Barren Fork downstream of the confluence of the North and South Prongs. Barrens Darters in MU 2 have only been found in the very headwaters of tributaries to the North Prong as well as in Dog Branch. The last time Barrens Darters were found in this MU was the early 1990s during the collecting efforts that resulted in the species description. The land cover in MU 2 is similar to that of MU 1, with the addition of development around Centertown, TN in the upper portion of Dog Branch. North Prong Barren Fork is significantly impacted by agricultural activities and urban land use in Centertown. These impacts have likely contributed to the Barrens Darter’s potential extirpation in MU 2. MU 3: McMahan and Lewis Creeks McMahan Creek and its tributary, Lewis Creek, are in the heart of the Barrens Darter’s range. Barrens Darters have consistently been collected within the headwater portions of McMahan and Lewis creeks, including areas that seasonally dry. The site where the highest number of Barrens Darters (69) were captured in a single collecting effort is in Lewis Creek, and most of these were juveniles. However, of the streams where Bergen et al. (2012, p. 438) studied the nesting biology of Barrens Darters, Lewis Creek had the highest egg fungal infection rate and nest failure rate. Less intensive farming occurs in MU 3 than in MUs 1 and 2, and there are no large nurseries in the watershed. There is also less development and more forested land draining to the creeks in MU 3. This MU is vulnerable to development of the community of Woodland, with much of the headwaters of McMahan Creek draining the Woodland Estates housing development. Although farming is less intensive, there is some potential for poor farming practices in MU 3 to have a negative impact on Barrens Darters. There is also the risk of potential spills from trucks travelling along TN 53, which crosses almost all of the tributaries of MU 3. Habitat and population elements in the McMahan and Lewis Creeks Management Unit are generally high. Therefore, in this MU current resilience is high (Table 4-2).

MU 4: Duke Creek Duke Creek is the type locality for the Barrens Darter and one of the strongholds for the species. Barrens Darters in varying numbers have been collected in Duke Creek across its survey history and numbers were highest in the most recent survey (Mattingly and Johansen, p. 5). This watershed is mostly in row crops and pasture with residential development throughout. Much like the other units, stream habitat in the Duke Creek watershed is affected by livestock and row crop agriculture, and it is under the risks associated with highway 53. Just across the divide in the Brawleys Fork watershed, a misapplication of a pesticide resulted in a fish and crayfish kill in 2013. Most habitat elements in Duke Creek are in moderate condition, whereas most population elements are in high condition. Therefore, in the Duke Creek Management Unit current resilience is high/moderate (Table 4-2) MU 5: South Prong Barren Fork The South Prong Unit includes Liberty Creek, Pocahontas Branch, and Mud Creek. Pocahontas Branch has consistently had good numbers of Barrens Darters in surveys over the past 25 years. Numbers in Liberty Creek have been low, and the species was not collected there in 2017 (Mattingly and Johansen 2017, p. 5). In Mud Creek, Barrens Darters have been replaced by Fringed Darters over the past fifteen years. Overall, there seems to be a decline in this unit. Most of the land cover for this unit is in row crop agriculture with some pasture land and nurseries. The riparian buffer for Pocahontas Branch and Liberty Creek appears to be relatively intact, but less pervasive on Mud Creek. There is a cattle feedlot on Liberty Creek without runoff treatment. During the current Barrens Darter survey, a landowner reported a fertilizer spill fifteen to twenty years ago that resulted in a fish kill in Liberty Creek (Hayden Mattingly, Jacob Hartman, pers. comm.) The South Prong Barren Fork MU shares many of the same threats as the other MUs, in addition to being vulnerable to Fringed Darters replacing Barrens Darters. Mud Creek may have been more prone to the invasion of Fringed Darters, due to its lower gradient making it more like a larger stream and more prone to drying. Most habitat and population elements in the South Prong Barren Fork Management Unit are in low condition. Therefore, in this MU current resilience is low (Table 4-2)

MU 6: West Fork Hickory Creek Barrens Darters were widespread in the West Fork Hickory Creek watershed based on museum collections, but the species has not been collected in this MU since 1982. Fringed Darters have replaced the Barrens Darters in this MU. Genetic analysis on tissue samples taken from Fringed Darters in this watershed has revealed evidence of past hybridization with of Barrens Darters females with Fringed Darter males. Heavily agricultural, with pasture, row crops and several nurseries present, the West Fork Hickory Creek watershed suffers from many of the same threats present in the other watersheds in the historical range of the Barrens Darter. There is a concentrated animal feeding operation on

Meadow Branch, which feeds directly to the creek. The large community of Summitville, which includes a golf course and is crossed by TN 55, is in the headwaters of this MU. Together, the effects of development, agriculture, and Fringed Darters have likely contributed to the Barrens Darter’s potential extirpation in MU 2. MU 7: Upper Collins River Watershed The upper Collins River Unit includes Savage Cove Creek, Taylor Creek, Pepper Hollow Branch as well as the mainstem Collins River and other tributaries upstream of the community of Irving College, Tennessee, roughly 40km (25mi.) upstream of the mouth of the Barren Fork. This unit was only recently verified to exist in the Spring of 2018. Prior to the collection of individuals in 2018, the only known record of spottail darters in the upper Collins River watershed was a single Barrens Darter collected from Scott Creek in 2003. The specimen was verified based on meristics, but a genetic sample was not taken. Since that time no other spottail darters have been found in Scott Creek, indicating that this creek may represent lost range. Most of these tributary streams are seasonally dry not far above the mainstem of the river, and the river itself is seasonal a few miles upstream of the mouth of Pepper Hollow Branch. Most of the land draining to the perennial portions of the streams are used for agriculture. The primary form of agriculture within this management unit is the nursery industry with some additional row crop and hay or pasture land cover present. This has resulted in modification of some of the streams in the watershed such as incision and heavy nutrient and sediment loads, such as those seen in Taylor Creek (Charles Walton, TDEC, pers. comm.). Limited surveys for Barrens Darters have taken place in the Upper Collins River watershed, resulting in limited data for this unit. There has been significant impacts to habitat in the unit, but overall the population metrics are doing well. Repeated efforts have failed to find Barrens Darters in the Scott Creek since the initial specimen found in 2003. Therefore, the current resilience in the Upper Collins River watershed is rated as moderate (Table 4-2). Other Sites Barrens Darters have been collected at an additional site outside of these MUs historically in Witty Creek. Witty Creek is formed by the joining of McMahan and Duke Creek. A single Barrens Darter was collected during a survey in 1994 (Madison 1995, entire), but none were collected in more recent surveys. Given the proximity to both McMahan and Duke Creeks, which have good numbers of Barrens Darters, and the larger size of Witty Creek at the site of collection, it is likely that this record represents a dispersing fish. Because the record is not from typical Barrens Darter small stream habitat, it shows the potential for migration between MUs.

Management Physical Water Population Approximate Occurrence Presence of Occurrence Resilience Unit Habitat Quality Complexity Abundance Extent Fringed Complexity Darters (Current) 1. Charles 133 Moderate Low 2.7 Moderate Moderate Low Low Creek Moderate/ Low Low 2. North Prong 101 Moderate Extirpated Extirpated Extirpated High Extirpated Extirpated Barren Fork Moderate/ Low 3. McMahan 164 Moderate High 47.7 Moderate High High High and Lewis High High Creeks 144 Moderate High 12.7 High High High High/ 4. Duke Creek Moderate Moderate Moderate

5. South Prong 143 Low Moderate 6.0 Low Low Low Low Barren Fork Moderate/ Low Low 6. West Fork Moderate Low Extirpated Extirpated Extirpated Extirpated Extirpated Extirpated Hickory Creek (FD replaced BD) 7. Upper 115 Low High 6.2 Moderate High High Moderate Collins River Moderate/ Moderate Low Table 4-2. Current resilience of Barrens Darter management units

Current Species Level Status 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 2000, p. 308). It is characterized by having multiple, resilient populations distributed throughout the species’ ecological setting and across its range. For a species to exhibit greater redundancy the populations should not be completely isolated and immigration and emigration between populations should be achievable. The Barrens Darter has low redundancy, because the species is a single genetic population with limited representation, and because its range contains four MUs, two of which are resilient. Some migration is still possible between streams within the Barrens Darter range; however, there are barriers to fish passage, primarily perched culverts that hinder migration in some streams, such as McMahan Creek. 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 2000, p. 308). The Barrens Darter does not exhibit high representation, due to its naturally narrow range in a single watershed within the same physiogeographic province. While this is the natural condition, we estimate that the Barrens Darter has low adaptive potential. There is very limited genetic diversity across the range of the species, with limited mutation from a common mitochondrial haplotype, and there is no evidence of geographic structuring across the range of the species, meaning that the whole species is represented by a single genetic population. Furthermore, the streams on the edges of the species range, where the most diversification would be expected, have declined or been extirpated. Chapter 5: Future Conditions In this chapter, we describe how current viability of the Barrens Darter may change over a period of 5 years and a period of 30 years. These time-steps were selected based on the availability of predictive models, such as SLEUTH, as well as the biology of the species, to show change across time. As in the Current Condition discussion, we evaluate species viability in terms of resilience at the population scale, and representation and redundancy at the species scale (3 Rs). 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 three main elements of change: development, conservation levels, and climate change. These scenarios capture the range of likely viability outcomes that the Barrens Darter will exhibit by 2050. Based on the SLEUTH urbanization model for the Barrens area, it is anticipated that there will be a significant increase in development in the headwater portions of the Barrens Darter range (Figure 5-1). Given the proximity to growing cities like Murfreesboro, McMinnville, and Tullahoma, the flat topography, and the availability of thoroughfares such as TN 53 and TN 55, 25

the Barrens Darter range is a prime area for development based on the SLEUTH model. The increase in impervious surfaces will result in flashier hydrology that will further degrade habitat. The increased population will also require more water, which will put a strain on the limited sources in the area. More development will bring with it higher levels of contaminants in runoff to the streams that could impact sensitive species (Diamond et al. 2016, entire). We vary the level of impact from development in the scenarios presented below. Conservation work in the Barrens area benefitting the Barrens Darter has been very limited. There have been some riparian buffer initiatives, but they are limited in scope. The Spottail Darter group is fairly easy to propagate in captivity, so it is a possibility that Barrens Darters could be reintroduced (JR Shute, pers. comm.) to help accomplish conservation in the future. However, if the factors leading to the loss of the species from an area have not been addressed, reintroduction will not be successful (George et al. 2009, pp. 539-540). In the Southeast, the clear trends in climate predictions are limited. Variability in weather is predicted to increase, resulting in more frequent and more extreme dry years and wet years over the next century, though increases in variability are already being seen (Mulholland et al. 1997, entire, Ingram et al. 2013, entire). Average and extreme temperatures are also expected to increase over time. More droughts will increase the likelihood that a Barrens Darter stream is impacted by reduced groundwater discharge, resulting in the reduction or elimination of populations. Droughts will also increase the reliance on groundwater for irrigation of crops in the Barrens and may force municipalities to use secondary water sources, which has the potential to further reduce stream discharge. More wet weather will result in more extreme flows, increased erosion, and stream incision, washing out and degrading habitat. This change in habitat could create more favorable conditions for the Fringed Darter. Warmer temperature will result in lower dissolved oxygen levels and could increase the risk of fungal or bacterial infection of Barrens Darter eggs. We use either little or no noticeable change in climate over our projected time span, moderate change in climate, or strongly noticeable change in climate in the prediction of our future scenarios.

Figure 5-1. SLEUTH Model showing anticipated extent of urban development in 2050. Black represents the current extent

of urban development and the darker the red, the higher the certainty of development. Barrens Darter range shown in green. Scenario 1 In Scenario 1 the developed area in the Barrens Darter range is expected to nearly double in the next 30 years, but with limited change within the next five years, based on the 95% confidence interval of the model. The current trends in climate continue with a severe drought and or flooding expected in the 5-year time frame, impacting some areas, and over 30 years, drought negatively affects marginal habitat areas. Under this scenario, conservation, in the form of a low level of riparian habitat improvement, is expected to occur, though this may be offset by the expansion of developed areas. Resilience MU 1: Charles Creek Under Scenario 1 the declining trend in Charles Creek is anticipated to continue, resulting in lower abundance, and a restriction in the distribution of Barrens Darters in the stream in the 5- year and 30-year terms. Habitat is expected to continue to degrade due to the flashy nature of the stream. In the long term, Fringed Darters are likely to take advantage of the change in habitat and colonize upstream of their current extent. The nursery industry is expected to continue to impact the middle and lower reaches of Charles Creek through contaminant runoff and high water use. The SLEUTH urbanization model predicts significant development of the Center Hill community in the very headwaters of the watershed, which is likely to increase flash flooding, disrupt habitat, and increase the level of contaminants in the entire stream, given the non-

dendritic (few branches) nature of this watershed. In the 30-year time frame, it is likely that the Barrens Darter will be extirpated from the Charles Creek watershed. Under Scenario 1, the threats acting on the Barrens Darter in the Charles Creek MU are anticipated to result in a change, from the low current resilience, to an extirpated future condition (Table 5-1). MU 2: North Prong Barren Fork Under Scenario 1, Centertown is expected to grow significantly based on the SLEUTH model, resulting in more urban impacts to Dog Branch in addition to the agricultural activities still happening in the watershed, as well as growth in the headwaters of the other component streams. This will increase the flashiness, further limiting the already limiting habitat in the watershed. Climate change will exacerbate this degradation over the next 30 years. Reintroducing the Barrens Darter to this watershed will not be a priority, and the poor habitat quality will make natural recolonization very unlikely. Therefore, resilience in MU 2 is not expected to change and it will be in an extirpated future condition (Table 5-1). MU 3: McMahan an Lewis Creeks McMahan and Lewis Creeks will likely change little in Scenario 1. However, since portions of these creeks go dry during late summer, and even more so during droughts, it is likely that climate change will reduce somewhat the overall extent of the Barrens Darter in this MU, at least part of the time. Furthermore, housing development within the McMahan and Lewis headwaters is likely to expand, and, over the 30 years, it is likely that TN 53 will be widened. This will have some negative impacts on habitat. Some of the potential stressors from agriculture and development may be reduced by conservation actions taken to protect the Barrens Darter in the headwaters of McMahan Creek, but it is still likely that habitat and abundance will decline slightly. Under Scenario 1, the threats acting on the Barrens Darter in the McMahan and Lewis Creek MU are anticipated to result in a change, from the high current resilience, to a high/moderate future resilience (Table 5-1). MU 4: Duke Creek Duke Creek is forecast to have expanded development in its headwaters and middle section in the Ivy Bluff and Hollow Springs communities. In Scenario 1, this is likely to result in degradation of habitat and water quality. It is unlikely that there will be a big change in overall condition; however, total survivability and occupied extent will likely decline. Under Scenario 1, the threats acting on the Barrens Darter in the Duke Creek MU are anticipated to result in a change, from a high/moderate current resilience, to a moderate future resilience (Table 5-1). MU 5: South Prong Barren Fork Under Scenario 1, a slight decline is anticipated in MU 5. Based on the SLEUTH model, there will be significant growth in the headwaters of Liberty Creek. This will likely result making the already marginal habitat in Liberty Creek unsuitable for Barrens Darters. The habitat in Pocahontas Branch will likely be degraded by continued farming. Fringed Darters will likely

take advantage of the loss in Liberty Creek and expand out of Mud Creek and into Liberty and possibly the lower portions of Pocahontas Branch.

Under Scenario 1, the threats acting on the Barrens Darter in the South Prong Barren Fork MU are not anticipated to result in a change, though there could be decline, and it will remain in a condition of low resilience in the future (Table 5-1). MU 6: West Fork Hickory Creek In the short term, West Fork Hickory Creek will continue to be impacted by the large community of Summitville and the nursery industry. By 2050, the development around Summitville is anticipated to extend along the TN 55 corridor between Tullahoma and McMinnville. This is likely to continue to negatively impact the habitat and water quality of this watershed such that is unlikely to for Barrens Darters to naturally reestablish. Therefore, resilience in MU 2 is not expected to change and it will be in an extirpated future condition (Table 5-1). MU 7: Upper Collins River Under Scenario 1, a slight decline is anticipated in the Upper Collins River watershed. Based on the SLEUTH model, MU 7 will see less development than the other units, but the impacts from agriculture are expected to continue in the near future. What development is predicted will occur on the Cumberland Plateau portion of the watershed around Beersheba Springs, upstream of the areas occupied by Barrens Darters and where the streams are intermittent. Because of the continued impacts from the nursery industry and other agriculture, we expect a moderate/low condition (Table 5-1).

Management Physical Water Population Approximate Occurrence Presence Occurrence Resilience Unit Habitat Quality Complexity Abundance Extent of Complexity Fringed Darters 1. Charles Low Low Extirpated Extirpated Extirpated Low Extirpated Extirpated Creek

2. North Prong Moderate/ Low Extirpated Extirpated Extirpated High Extirpated Extirpated Barren Fork Low

3. McMahan Moderate Moderate High Moderate Moderate High High Moderate/ and Lewis High Creeks Moderate Moderate Moderate Moderate Moderate High High Moderate 4. Duke Creek

5. South Prong Low Low Moderate Low Low Low Low Low Barren Fork

6. West Fork Moderate Low Extirpated Extirpated Extirpated Low Extirpated Extirpated Hickory Creek

7. Upper Low Low Moderate Low Low Moderate High Moderate/ Collins River Low

Table 5-1. Resilience under Scenario 1.

Redundancy Under Scenario 1, the Barrens Darter will have low redundancy due to the loss of one MU and the reduction in the resilience in the remaining extant MUs. Representation The Barrens Darter will continue to have low representation under scenario 1, since it is one genetic population. The loss of more individuals and Management Units further reduces the adaptive potential of the species. It is likely in this scenario that the lower portions of occupied habitat in some of the extant streams will be lost, reducing the possibility of movement between units. Scenario 2 Scenario 2 shares similar levels of development with Scenario 1, but with implementation of additional precautions to reduce impacts to streams. This scenario also takes into account a greater level of riparian conservation efforts. This will help to mitigate changes in climate that would negatively affect the Barrens Darter to some degree. Under this scenario, efforts will also be made to propagate and reintroduce Barrens Darters into suitable, available habitat. Resilience MU 1: Charles Creek Through the implementation of widespread riparian protection in this scenario, the flashy hydrograph of Charles Creek could be mitigated. This effort would also maintain cooler water temperatures. These changes could reduce the likelihood of further expansion of Fringed Darters in the watershed. The improved habitat would likely improve the abundance and survival of Barrens Darters in this watershed, though in a limited fashion because much of the past alteration of Charles Creek has resulted in the elimination of potential habitat. Under Scenario 2, the threats acting on the Barrens Darter in the Charles Creek MU are anticipated to result in a positive change, from the low current resilience, to a moderate future resilience (Table 5-2). MU 2: North Prong Barren Fork Intensive habitat improvement efforts may restore the habitability of a portion of this unit for Barrens Darters under Scenario 2. Given the current absence of Fringed Darters and multiple streams in this unit that provide opportunity to increase occurrence complexity, MU 2 would be a logical place to attempt reintroductions, although success is not certain. Under Scenario 2, the threats acting on the Barrens Darter in the Charles Creek MU are anticipated to result in a positive change, from the extirpated current condition, to a low future resilience (Table 5-2). MU 3: McMahan and Lewis Creeks Scenario 2 would provide improved riparian buffers in this watershed so that it would maintain the good quality currently present, and help offset the effects of climate change. Under this scenario, efforts would be made to address water quality issues in this MU as well.

Under Scenario 2, the threats acting on the Barrens Darter in the McMahan and Lewis Creeks MU are not anticipated to result in a change, and it will remain in a condition of high resilience in the future (Table 5-2).

MU 4: Duke Creek Improvements to habitat may help boost Barrens Darter numbers in the Duke Creek MU under Scenario 2, and efforts will help maintain and improve the stream quality of the area.

Under Scenario 2, the threats acting on the Barrens Darter in the Duke Creek MU are anticipated to result in a positive change, from the high/moderate resilience, to a high future resilience (Table 5-2)

MU 5: South Prong Barren Fork Expansion of residential development will be conducted in a responsible manner, and conservation will help improve habitat in some portions of MU 5 under Scenario 2. Because of the presence of Fringed Darters in this MU, it may not be possible for Barrens Darters to recover fully on their own.

Under Scenario 2, the threats acting on the Barrens Darter in the South Prong Barren Fork MU are not anticipated to result in a change, and it will remain in a condition of low resilience in the future (Table 5-2).

MU 6: West Fork Hickory Creek Conservation actions in this MU will help improve water quality and habitat, but the widespread establishment of Fringed Darters in the West Fork Hickory Creek MU creates a less than optimal environment for reintroduction. Therefore, resilience in MU 6 is not expected to change and it will be in an extirpated future condition (Table 5-2)

MU 7: Upper Collins River Increases in riparian protection in the tributaries to the Upper Collins River will help to improve in stream habitat by reducing sediment inputs. Direct efforts to address the water quality and quantity issues associated with the nursery industry in MU 7 would provide benefit to the Fringed Darter and would likely result in increased numbers. Under Scenario 2, some of the threats to the Barrens Darters in MU 7 would be addressed, resulting in an improvement in the resilience of this MU. Because of this improvement, the condition of MU 7 would rise to high (Table 5-2).

Management Physical Water Population Approximate Occurrence Presence Occurrence Resilience Unit Habitat Quality Complexity Abundance Extent of Fringed Complexity Darters 1. Charles Moderate/ Moderate Moderate Moderate Moderate Moderate Low Moderate Creek Low

2. North Prong Moderate/ Moderate Low Low Low High Low Low Barren Fork Low

3. McMahan High Moderate High High Moderate High High High and Lewis Creeks Moderate Moderate High High High High High High 4. Duke Creek

5. South Prong Moderate/ Low Moderate Moderate Low Low Low Low Barren Fork Low

6. West Fork Moderate Moderate Extirpated Extirpated Extirpated Extirpated Extirpated Extirpated Hickory Creek

7. Upper Moderate Moderate High High Moderate High High High Collins River

Table 5-2. Resilience under Scenario 2.

Representation Under Scenario 2, the Barrens Darter will have low representation because of the single genetic population present. This scenario will likely maintain what adaptive potential there is for the species currently. It is unlikely that movement between MUs will change under this scenario. Redundancy Under Scenario 2, resilience of some MUs will improve, especially with the reestablishment of MU 2. There will be two fully resilient units and a moderately resilient unit improved from its current low condition. Additionally one previously extirpated unit will have an established group of reintroduced Barrens Darters. All of the units are still vulnerable to stochastic events such as contaminant spills, but such events would be very unlikely to affect more than one unit at a time. Under Scenario 2 the Barrens Darter will have moderate redundancy. Scenario 3 In Scenario 3, effects from climate change and development will not be offset by a meaningful amount of conservation. Development will take place at the level projected by the 85% confidence level in the SLEUTH model. Water quality and quantity will continue to be degraded by nurseries, row crops, and livestock rearing. More intense and frequent droughts associated with climate change will reduce discharge in the Barrens Darter’s habitat and increase the water demands of agriculture in the area. Development will contribute to habitat degradation and contaminant spills in the Barrens area. Conservation efforts under this scenario will be minimal and will not make a significant difference in curtailing threats. Resilience MU 1: Charles Creek The declining trend in Charles Creek is anticipated to continue under Scenario 3, resulting in lower abundance, and a restriction in the distribution of Barrens Darters in the stream in the 5-year and 30-year terms. Habitat is expected to continue to degrade due to the flashy nature of the stream. In the long term, Fringed Darters are likely to take advantage of the change in habitat and colonize upstream of their current extent. The nursery industry is expected to continue to negatively impact the middle and lower reaches of Charles Creek through contaminant runoff and high water use. The SLEUTH urbanization model predicts significant development of the Center Hill community in the very headwaters of the watershed, which is likely to increase the flashiness, disrupt the habitat, and increase the level of contaminants in the entire stream given the non-dendritic (few branches) nature of this watershed. In the 30-year time frame, it is likely that the Barrens Darter will be extirpated from the Charles Creek watershed.

Under Scenario 3, the threats acting on the Barrens Darter in the Charles Creek MU are anticipated to result in a change, from the low current resilience, to an extirpated future condition (Table 5-3).

MU 2: North Prong Barren Fork Under Scenario 3, Centertown is expected to grow significantly based on the SLEUTH model, resulting in more urban impacts to Dog Branch in addition to the agricultural impacts still happening in the watershed, as well as growth in the headwaters of the other component streams.

This will increase the flashiness of the hydrograph, further limiting the already limiting habitat in the watershed. Climate change will exacerbate this degradation over the next 30 years. Reintroducing the Barrens Darter to this watershed will not be a priority, and the poor habitat quality will make natural recolonization very unlikely. Therefore, resilience in MU 2 is not expected to change and it will be in an extirpated future condition (Table 5-3).

MU 3: McMahan an Lewis Creeks Under this scenario, drought will impact the upper portions of the streams. This will make Lewis Creek more susceptible to the impacts associated with the existing issues with livestock waste. McMahan Creek is vulnerable to spills from agricultural chemicals, similar to the events in Liberty Creek and Brawleys Fork, due to the large amount of row crop activity in the very headwaters of the stream. This stream is also at risk from contaminants in transit that could spill into the stream at the TN 53 crossing. This will result in a significant decline in the condition of the Barrens Darters in this MU.

Under Scenario 3, the threats acting on the Barrens Darter in the McMahan and Lewis Creek MU are anticipated to result in a change, from the high current resilience, to a low future resilience (Table 5-3).

MU 4: Duke Creek In addition to the present agricultural risks in the Duke Creek watershed, predicted development will greatly degrade the habitat and water quality in the MU. Little will be done to offset these threats. The increased development will exacerbate the effects of climate change on habitat quality by increasing the flashiness and worsening the effects of drought. These habitat effects will reduce the numbers of Barrens Darters significantly in this MU.

Under Scenario 3, the threats acting on the Barrens Darter in the Duke Creek MU are anticipated to result in a change, from the high/moderate current resilience, to a low future resilience (Table 5-3).

MU 5: South Prong Barren Fork A significant decline is anticipated in MU 5. Based on the SLEUTH model, there will be considerable growth in the headwaters of Liberty Creek. This will make the already marginal habitat in Liberty Creek unsuitable for Barrens Darters, and favor the expansion of Fringed Darters. The habitat in Pocahontas Branch will be degraded by continuation of poor farming practices that will be exacerbated by climate change over the next 30 years. Fringed Darters will take advantage of the loss in Liberty Creek and expand out of Mud Creek and into Liberty and Pocahontas Branch. The combinations of these threats will result in the extirpation of Barrens Darters from MU 5.

Under Scenario 3, the threats acting on the Barrens Darter in the South Prong Barren Fork MU are anticipated to result in a change, from the low current resilience, to an extirpated future condition (Table 5-3).

MU 6: West Fork Hickory Creek In the short term, West Fork Hickory Creek will continue to be impacted by the large community of Summitville and the nursery industry under Scenario 3. By 2050, the development around Summitville is anticipated to extend along the TN 55 corridor between Tullahoma and McMinnville. This will continue to negatively impact the habitat and water quality of this watershed such that is unlikely that Barrens Darters could naturally reestablish. Therefore, resilience in the West Fork Hickory Creek MU is not expected to change and it will be in an extirpated future condition (Table 5-3).

MU 7: Upper Collins River Under Scenario 3, the threats from agriculture would be exacerbated. Increases in runoff and sedimentation from nursery and row crop agriculture in the watershed would result in the extirpation of Barrens Darters in some of the tributaries.

Management Physical Water Population Approximate Occurrence Presence Occurrence Resilience Unit Habitat Quality Complexity Abundance Extent of Fringed Complexity Darters 1. Charles Low Low Extirpated Extirpated Extirpated Low Extirpated Extirpated Creek

2. North Prong Low Low Extirpated Extirpated Extirpated High Extirpated Extirpated Barren Fork

3. McMahan Low Low Moderate Low Low High Moderate Low and Lewis Creeks Low Low Low Low Low High Moderate Low 4. Duke Creek

5. South Prong Low Low Extirpated Extirpated Extirpated Low Extirpated Extirpated Barren Fork

6. West Fork Moderate Low Extirpated Extirpated Extirpated Low Extirpated Extirpated Hickory Creek

Table 5-3. Resilience under Scenario 3.

Redundancy In Scenario 3, the Barrens Darter will exhibit very low redundancy because there are no resilient MUs, only two of which are expected to persist. The remaining Barrens Darters would be extremely vulnerable to any perturbations in their environment. Representation The loss of large portion of the single genetic population under Scenario 3 would result in a bottlenecking of the Barrens Darter. The species would exhibit very low representation due to the very limited adaptive potential of the species at this point. Status Summary Future viability The future scenario assessment has sought to understand how viability of the Barrens Darter may change over the course of 20-30 years in the terms of resilience, redundancy, and representation. To account for considerable uncertainty associated with future projections, we defined three plausible scenarios that would capture the breadth of changes on the Barrens Plateau to which the Barrens Darter may be exposed. These scenarios considered three elements of change: development, levels of conservation effort, and climate change. 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, probability categories (Table 5-4) were used to describe the likelihood a scenario will occur (Table 5-5).

Confidence Terminology Explanation (Probability Category) 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 5-4. Explanation of confidence terminologies used to estimate the likelihood of a scenario (after IPCC guidance, Mastrandrea et al. 2011).

Scenario 1 2 3 5 years Very Likely Unlikely As likely as not 30 years Likely Unlikely As likely as not Table 5-5. Likelihood of a scenario occurring at 5 and 30 years. In Scenario 1 we predicted that development would take place at the level projected by the SLEUTH model at the 95% confidence level, climate would continue at current trends, and conservation efforts would occur, but in a limited way. Based on these criteria, it was anticipated that the Charles Creek MU would be extirpated, and the extant MUs would be reduced in resilience. This would leave three extant MUs: two with Moderate resilience and one with low resilience. This scenario is considered likely given past levels of conservation in the area and the current farming and development practices.

Under Scenario 2, the range of the Barrens Darter would undergo similar levels of development as Scenario 1, but the development would be carried out in a responsible manner. This scenario also takes a high level of conservation into account that would help to undo current habitat damage and reintroduce Barrens Darters back into at least one stream where they are extirpated. These efforts are predicted to result in five extant MUs: two with High resilience, one with Moderate resilience, and two with Low resilience. This scenario is considered unlikely because changes in farming and development practices without legislation are unlikely to take place in Tennessee. This area has also had little conservation work at the landscape scale, which would be necessary to see the positive effects predicted here. Scenario 3 anticipates that development will occur at a higher level than predicted in the other two scenarios, agricultural practices will remain the same, climate change will exacerbate the effects of the other stressors, and conservation will not occur at a level necessary to counteract the stresses on the habitats of the Barrens Darter. This scenario also incorporates a higher risk of a chemical spill of some kind. This will result in the extirpation of all but two MUs, and these will both have Low resilience. This scenario is expected to be as likely as not to occur because of the limited efforts at conservation in the Barrens area, the recent passage of a Tennessee law reducing regulation of livestock operations in the state (Chapter 293 of the Public Acts of 2018), and history of recent agricultural spills. Because the effects of climate at the 30-year time horizon will be in early manifestation, our confidence Scenario 3 transpiring was less than for Scenario 1. Uncertainty Our analysis of current and future conditions contains uncertainty because we are unable to know the exact current status of the Barrens Darter and our future scenarios are projections based only on current trends. The following are uncertainties recognized in the report: • Because of limited access to streams on private property, it is unclear what the true full extent of the species is within the occupied creeks. • There is limited ability to predict future agricultural activities. • It is unclear what specifically led to the extirpation of MU 2. • We are uncertain why Fringed Darters have replaced Barrens Darters within MU 6. • The genetic data currently available cannot determine when hybridization occurred between Barrens Darters and Fringed Darters. • It is not known whether there is geographic structuring in the nuclear genes of the Barrens Darter. • Annual persistence and approximate abundance of Barrens Darters in the vicinity of the Scott Creek and Collins River confluence is not known. • Because of the similarity of Barrens Darters and Fringed Darters, there is some uncertainty in the identifications from some past surveys; however, for current condition, this report focuses on surveys with verified voucher specimens or males in the collection. • The specific habitat needed by the species as juveniles and non-spawning adults has not been classified.

Overall Summary Currently, the Barrens Darter is known only from the headwaters of the Barren Fork and a direct tributary of the Collins River. The whole range is represented only by a single genetic population, but due to the limited amount of movement between streams, has been divided into 6 MUs for the purpose of analysis. The Barrens Darter has been extirpated from two of these units (33% loss). Two of the extant MUs currently exhibit high resilience. The other two extant MUs have low resilience. The predominant threat to this species is degradation of habitat associated with residential development and nursery, row crop, and livestock agriculture. The changes to habitat appear to make portions of streams previously inhabited by Barrens Darters more suitable for the closely related Fringed Darter. Our future scenarios assessment considered the current viability of the species to project likely future viability given plausible scenarios of development, conservation efforts, and climate change. Only under Scenario 2 did the Barrens Darter persist in all currently occupied MUs. However, this scenario relied most on increased application of measures to protect habitat during development and increases in applied conservation, making it the least likely. Under Scenario 1, the most likely of the three scenarios, the redundancy and representation of the species remained low because the limited genetic viability and distribution on the species. Scenario 1 resulted in the loss of one MU, leaving two moderate MUs and one low MU. This loss further reduces the redundancy and representation of the species. Under Scenario 3, all but the two most currently resilient MUs will be extirpated, leaving the species’ range with two MUs that have low resilience, and nearly eliminating the representation and redundancy of the species.

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