Species Status Assessment Report for the Amber Darter Percina antesella Williams and Etnier 1977
Department of the Interior South Atlantic-Gulf Region
Georgia Ecological Services Field Office Athens, Georgia
November 2019
This species status assessment report provides the best available information on the ecological requirements, current conditions, threats/stressors, future needs, and conservation actions for the endangered amber darter (Percina antesella). Updates to this version are anticipated as additional information becomes available.
Robin Goodloe (USFWS-Georgia Field Office) prepared the document, with assistance from Dr. Brett Albanese, Paula Marcinek, and Ani Popp (Georgia Department of Natural Resources); Dr. Mary Freeman (USGS); Edward Sage Stowe (University of Georgia); and Erin Rivenbark (USFWS-Region 4). We appreciate their time and effort to make this a more robust assessment and final report.
Suggested Citation:
U.S. Fish and Wildlife Service. 2019. Species status assessment report for amber darter (Percina antesella). South Atlantic-Gulf Region, Georgia Ecological Services, Athens, GA.
Copies may be obtained from: U.S. Fish and Wildlife Service Georgia Ecological Services Office RG Stephens Federal Building 355 E. Hancock Ave., Room 320, Box 7 Athens, Georgia 30601 706-613-9493 Available online at the US Fish and Wildlife Service Catalog, https://ecos.fws.gov/ServCat/.
Amber Darter SSA Page i Executive Summary The amber darter (Percina antesella) occurs in the Etowah and Conasauga Rivers of Georgia and Tennessee. These small fish generally are found in the rivers’ mainstems, preferring shoals with a moveable gravel/small cobble substrate and moderate to swift currents. Primary factors affecting the species’ include: (1) habitat degradation associated with agriculture, (2) urban sprawl of the Atlanta metropolitan area, (3) small population size and limited geographic range, and (4) climate change.
We used the best available information to evaluate the current viability of the amber darter in terms of its resiliency, redundancy, and representation. Count data from surveys over almost two decades indicate numbers of amber darters in both populations are declining, with estimated losses of 12% and 9% annually in the Conasauga and Etowah Rivers. Occupancy of shoals has decreased in the Conasauga, and fish have been extirpated or greatly reduced in abundance in the lower reaches of the historic range in both systems. Declining populations suggest the species, currently, has low resiliency to environmental or demographic stochastic events and/or existing anthropogenic-related stressors.
Amber darter current conditions (resiliency). Population Annual Abundance Change over 20 Years1 Historic Range Occupancy 12% 50% Conasauga Very low Very low 9% Only 1 fish found in lower third of range Etowah during last 2 surveys Low Low 1 Based on MARSS analysis (Stowe et al. 2019).
Mitochondrial genetic variation is low in both populations, but high levels of genetic diversity were found within and between the two amber darter populations at six nuclear microsatellite markers; diversity was lower in the Etowah River than in the Conasauga, suggesting a recent bottleneck in population. The two amber darter populations are effectively isolated by Lake Allatoona, a 12,000- acre U.S. Army Corps of Engineers reservoir that bisects the Etowah River, reducing redundancy.
Preliminary results from viability models suggest that, at current rates of decline, amber darters would be effectively undetectable (defined as a catch-per-unit-effort of 1 fish in 400 seine-sets at a given shoal by experienced field biologists) between 2021 and 2032 in the Conasauga, and between 2030 and 2047 in the Etowah. A catastrophic event, such as a major flood that limits recruitment by washing eggs, larvae, and/or juveniles far downstream, could cause the species to decline even more rapidly. Species recovery could be enhanced if (1) a new viable population is located or established; (2) connectivity and genetic exchange are improved; and/or (3) stressors are reduced and habitat quality is improved so that recruitment of juveniles increases during favorable spawning years and survival of adults exceeds mortality. Habitat improvements must be made at a large enough scale, on priority tracts, and within a reasonable time period, to recover this species.
Amber Darter SSA Page ii Summary of amber darter needs, current conditions, and viability to 2060. Future Viability Current Current Stressor Species Needs Conditions and High Spring Best Case Scenario Flow Scenarios Resiliency: Large populations able to withstand stochastic events High quality shoal Narrow endemic Viability models Resiliency dependent habitat with areas of species with only two suggest that, at on (1) funding levels; moderate water small populations and current rates of (2) scale of depth flowing over limited geographical decline, amber implemented substrate dominated ranges. Count data darters would be management actions by moveable gravel from surveys over effectively relative to watershed and small cobble. almost two decades undetectable size and degree of Adequate water indicate both are between 2021 and threat; (3) ongoing quality and food declining 9-12% 2032 in the stochastic stressors; (4) availability. annually. Occupancy Conasauga, and how quickly Sexually-mature of shoals has declined 2030 and 2047 in the management actions are males and females in in the Conasauga, and Etowah. implemented; and (5) a shoal. Low spring fish in both systems the effects of climate flows for spawning. have been extirpated change on species’ Connectivity among or greatly reduced in demographics. shoals. Sufficient abundance in the numbers to lower reaches of the withstand stochastic historic range. events. Resiliency = low to very low. Redundancy: Number and distribution of populations to withstand catastrophic events Multiple resilient Only two With only two Redundancy dependent populations widely populations are populations, both in on (1) increased distributed across known historically, decline, redundancy resiliency of Conasauga the species’ historic and neither appears is likely to remain and Etowah populations range. resilient to stochastic low, unless viable (see above) and (2) or catastrophic populations are potential for locating events and/or to located or and conserving existing current established outside populations outside of anthropogenic of the species’ the Conasauga and stressors. known historical Etowah systems. range. Redundancy = low. Representation: Genetic and ecological diversity to maintain adaptive potential Decreased inbreeding Two declining Genetic diversity Genetic diversity likely and reduced negative populations likely to decline as to decline due to genetic impact of genetic drift genetically-isolated population numbers isolation unless and deleterious by Lake Allatoona. are reduced and Allatoona Dam is mutations on viability. genetic isolation removed and/or Representation = remains. individuals are Low to Moderate translocated between the two populations.
Amber Darter SSA Page iii Table of Contents
Introduction ...... 1 Amber Darter Needs Historic Distribution ...... 4 Taxonomy and Description ...... 6 Natural History ...... 7 Population Needs ...... 9 Species Needs ...... 9 Current Condition and Species’ Needs for Viability Current Population Trends ...... 11 Current Species Viability Current Resiliency ...... 14 Current Representation ...... 15 Current Redundancy ...... 16 Summary ...... 17 Factors Influencing Viability Small Populations and Limited Geographic Range ...... 18 Anthropogenic Stressors Historic Land Use ...... 19 Current Land Use in the Upper Conasauga River Basin ...... 20 Current Land Use in the Upper Etowah River Basin ...... 23 Stressors in the Conasauga and Etowah Basins Fine Sediment ...... 25 Excess Nutrients/Cultural Eutrophication ...... 26 Increased Impervious Surface Associated with Urbanization ...... 28 Glyphosate-Based Herbicides ...... 33 Lack/Removal of Riparian Buffers ...... 35 Decline in Abundance of Podostemum ...... 37 Reservoirs and Dams ...... 38 Climate Change ...... 39 Conservation Actions ...... 41
Amber Darter SSA Page iv Amber Darter Future Conditions: Viability to 2060 Scenarios ...... 44 Assumptions ...... 44 Current Stressor/Conservation Action Scenario ...... 44 Current Stressor/Conservation Action with High Spring Flow Scenario...... 44 Best Case Scenario ...... 45 Summary ...... 46 Literature Cited ...... 48
Tables
Table 1. Overview of amber darter individual, population, and species needs ...... 10 Table 2. Population characteristics used to create condition categories in Table 3 ...... 15 Table 3. Amber darter current conditions (resiliency) ...... 15 Table 4. Changes in agricultural land use and production in Murray and Whitfield Counties, Georgia, 1934-2017 ...... 21 Table 5. Changes in agricultural land use and production in counties of the Upper Etowah River watershed, Georgia, 1934-2012 ...... 23 Table 6. Population growth 1970-2017 and anticipated growth to 2050 in the Upper Etowah River Basin, Georgia...... 24 Table 7. Likely anthropomorphic stressors for amber darters ...... 25 Table 8. Sources of contaminants in urban stormwater runoff ...... 31 Table 9. Glyphosate-based herbicides and their surfactants ...... 33 Table 10. Conservation lands on or immediately adjacent to the Conasauga and Etowah River mainstems ...... 43 Table 11. Summary of amber darter needs, current conditions, and viability to 2060 ...... 47
Amber Darter SSA Page v Figures
Figure 1. Location of the Conasauga and Etowah Rivers in the Mobile River Basin...... 1 Figure 2. The amber darter’s known range in 1985 in the Conasauga River, TN and GA ...... 4 Figure 3. The amber darter’s known range, post-impoundment of Lake Allatoona, in the Upper Etowah River ...... 5 Figure 4. Amber darters ...... 6 Figure 5. Amber darter habitat ...... 7 Figure 6. Mean number of amber darters collected per shoal in the Conasauga 1996-2018 ...... 11 Figure 7. Mean number of individuals collected per shoal for three non-listed, but declining, fish species in the Conasauga ...... 11 Figure 8. Historic amber darter range in the Conasauga per-1995 vs current known range ...... 12 Figure 9. Amber darter sample locations in the Etowah River ...... 13 Figure 10. Mean number of amber darters collected per shoal in the upper two-thirds of the amber darter range in the Etowah River (Sites 1-10) ...... 13 Figure 11. Timing of erosive land use in the Southern Piedmont ...... 20 Figure 12. Drainage ditches, some dozens of feet wide, convey pollutants in stormwater runoff directly into the Conasauga ...... 21 Figure 13. Effects of agricultural drainage on aquatic ecosystems ...... 22 Figure 14. Average annual population change projected for Georgia counties, 2010-2030 ...... 24 Figure 15. Impervious surfaces alter the hydrologic cycle ...... 28 Figure 16. Impacts of urbanization on downstream base and peak flows ...... 30 Figure 17. Channel changes associated with urbanization ...... 30 Figure 18. Occurrence probability for bronze and amber darters in response to increasing EIA ...... 32 Figure 19. Conceptual model of urban impacts on streams ...... 32 Figure 20. Transport and degradation of glyphosate in agricultural landscapes ...... 35 Figure 21. Location of the riparian zone ...... 36 Figure 22. Podostemum on large cobble ...... 37 Figure 23. Etowah River hydrograph from US gage 02394670 downstream of Allatoona Dam ...... 38 Figure 24. Projected changes in US annual average temperatures ...... 40 Figure 25. Projected urban land cover in the Southeast US in 2060 ...... 44
Amber Darter SSA Page vi INTRODUCTION
The amber darter (Percina antesella) occurs in the Etowah and Conasauga Rivers of Georgia and Tennessee (Figure 1). Both are tributaries to the Coosa River in the biologically-diverse Mobile River Basin. These small fish generally are found in the rivers’ mainstems, preferring shoals with a moveable gravel/small cobble substrate and moderate to swift currents (Freeman and Freeman 1994). Survey data from over two decades indicate both populations are declining. Current stressors include: (1) habitat degradation associated with agriculture and past timber harvest, (2) urbanization, (3) small population size and limited geographic range, and (4) climate change. The US Fish and Wildlife Service (USFWS) listed the fish as endangered and identified critical habitat in the Conasauga River on August 5, 1985.
This Species Status Assessment (SSA) Figure 1. Location of the Conasauga and Etowah Rivers in the evaluates the amber darter’s future Mobile River Basin. The amber darter’s known historic range is in red (area circled). viability, based on the best available scientific information on the species and its stressors. The SSA framework involves three assessment stages:
1. Amber Darter Needs: The first stage is a compilation of the best available biological information on the species (taxonomy, life history, and habitat) and its ecological needs at the individual, population, and species levels based on how environmental factors are understood to act on the species and its habitat.
2. Amber Darter Current Condition: The next stage describes the current condition of the species’ habitat, demographics, and natural and anthropogenic stressors influencing past and ongoing changes in amber darter abundance and distribution. This section summarizes data provided in (1) reports on fish community and water quality data collected at shoals in suitable habitat in the Conasauga (1996-2018) and Etowah (1998-2017), (2) evaluation of population trends and habitat modifications, and (3) published literature, white papers, and annual and final research reports evaluating threats to fish communities in the basins. This
Amber Darter SSA Page 1 section includes a review of ongoing aquatic protection and management in the Conasauga and Etowah River basins by conservation partners.
3. Amber Darter Future Condition: In the last stage, the SSA forecasts the species’ response to probable future scenarios of environmental conditions and conservation efforts.
This document will be updated and peer-reviewed regularly to keep it current with the best available science. It is not a decision document -- it is an analytical tool that summarizes biological and ecological information to help inform Endangered Species Act decisions and activities, including recovery planning, five-year reviews, inter-agency consultations, and reclassifications. Recovery plans and recovery implementation schedules are separate documents from the SSA.
Analytical Framework for the SSA We defined viability as the ability of the amber darter to maintain self-sustaining populations throughout the species’ historic range in both the Conasauga and Etowah Rivers through 2060. Self- sustaining populations are those that are sufficiently abundant and have sufficient genetic diversity to display the array of life-history strategies that will provide for their persistence and adaptability over time (Committee of Scientists 1999) and in the face of environmental stochasticity, catastrophes, and changes in the biological and physical environment. We chose the timeframe to match a SLEUTH model that projected 2060 urban growth patterns for the Southeast U.S.
Using the SSA framework, we considered what the amber darter needs to maintain viability by characterizing the status of the species in terms of its resiliency, redundancy, and representation:
1. Resiliency describes the ability of a species to withstand either periodic or stochastic disturbance events, including environmental variation, demographic and genetic stochasticity, and anthropogenic stressors. Environmental variation includes normal year-to-year variation in rainfall and temperatures, as well as weather extremes, like flooding and drought, which can cause substantial changes to the structure or resources of an ecosystem. Demographic stochasticity refers to the variability in population growth rates arising from random differences among individuals in survival and reproduction probability within a season; demographic stochasticity generally is important only in populations that are already fairly small. Genetic stochasticity also primarily impacts small populations, generally causing loss of genetic variation through genetic drift and inbreeding, especially when population fragmentation disrupts gene flow. Anthropogenic stressors include human-caused factors that degrade and/or fragment habitat.
The primary indicators of resiliency that we evaluated in this SSA were amber darter abundance and distribution within the fish’s historic range in the Conasauga and Etowah River basins.
Amber Darter SSA Page 2 2. Redundancy is the ability of a species, as a whole, to withstand catastrophic events by having multiple populations widely distributed across its range. Having multiple, connected, resilient, representative populations distributed across the range of the species makes it less likely that single or multiple catastrophic events will cause the species’ extinction or significant loss of adaptive diversity and evolutionary flexibility. Connectivity allows for immigration and emigration between populations and increases the likelihood of recolonization should a population be extirpated.
3. Representation describes the ability of a species to adapt to changing environmental conditions and is measured by the breadth of genetic or environmental diversity within and among populations. Genetic diversity is the number and frequency of unique alleles within and among populations. Ecological diversity is the physiological, ecological, and behavioral variation exhibited by a species across its range. By maintaining these two sources of adaptive diversity across a species’ range, the responsiveness and adaptability of a species over time is preserved, which increases overall viability.
Amber Darter SSA Page 3 AMBER DARTER NEEDS
Historic Distribution The amber darter first was 1 collected in 1948 in Shoal Creek, 2
an Etowah River tributary in TN Cherokee County, Georgia, but was not seen again until 20 years GA
later, in 1968, when University of Tennessee personnel collected 3 it in the Conasauga River (Freeman 1983). The fish’s range in the Conasauga when it 4 was listed in 1985 extended over a 33.5-mile reach in the middle 5 section of the 93-mile long river
(Figure 2), from downstream of 6 the US 411 bridge in Tennessee to Tibbs Bridge Road, Murray and Whitfield County, Georgia (USFWS 1985). Historically, the amber darter likely occurred downstream of Tibbs Bridge but has been extirpated from this
reach, possibly due to increased Figure 2. The amber darter’s known range in 1985 (red dots) in the silt loads in shoal habitat Conasauga River, TN and GA (figure modified from Freeman et al. 2004). (USFWS 1985). The species’ Significant locations referenced in the SSA are: 1 = US Hwy 411, 2 = TN Hwy 74, 3 = GA Hwy 2 at Beaverdale, preference for gentle riffles may 4 = GA Hwy 286, 5 = US Hwy 76, and 6 = Tibbs Bridge Road. limit its distribution upstream, where channel slope is greater and there is a cooler, montane habitat (Freeman 1983).
The amber darter was rediscovered in the Etowah basin in 1980, 38 years after its initial discovery, when a single fish was found in the mainstem above Lake Allatoona (Freeman 1983). Intensive searches failed to locate additional individuals, and the 1985 Federal Register listing document concluded that an Etowah population, if it existed, was very small (USFWS 1985). Finally, in 1990, Alabama Power Company personnel captured amber darters at two sites in the Etowah mainstem above Lake Allatoona in Cherokee County, and a joint effort later that year by the University of Georgia and USFWS collected 24 individuals at 3 of 10 mainstem sample sites in Dawson, Forsyth, and Cherokee Counties, Georgia (Freeman 1990). Since then, amber darters have been collected at multiple shoals in a 28-mile reach of the mainstem Etowah River from just above its confluence with Amicalola Creek in the Dawson Forest Wildlife Management Area downstream to where the Etowah is impounded as Lake Allatoona (Figure 3). Freeman et al. (2012) suggested that, before the
Amber Darter SSA Page 4 U.S. Army Corps of Engineers constructed Lake Allatoona in 1950, amber darters may have existed continuously through the Conasauga, Oostanaula, and Etowah Rivers.
1
2 4
3
Figure 3. The amber darter’s known range (yellow circles), post-impoundment of Lake Allatoona, in the Upper Etowah River basin (figure from Etowah Aquatic Habitat Conservation Plan Steering Committee 2007). Locations referenced in the SSA are: 1 = Amicalola Creek, 2 = Sharp Mountain Creek, 3 = Shoal Creek, and 4 = Lake Allatoona.
The amber darter has been recollected in Shoal Creek only once, in 1993, since its 1948 discovery; individuals were reproducing (Gerald Dinkins, University of Tennessee, pers. comm. September 2018), but it was not determined if the sub-population was self-supporting. The species also was located once, in 1990, in the lowest reaches of Sharp Mountain Creek.
A single amber darter was collected in the Coosawattee River downstream of Carters Lake in 2010, but no individuals were found at 10 other shoals sampled that year (Brett Albanese, Georgia Department of Natural Resources, pers. comm. January 2011). Freeman (1983) conducted an extensive survey of fishes in the Coosawattee 1982-1983, including a review of historic collections, and found no amber darters. Single amber darters have been found upstream of their historic range in both the Conasauga and Etowah Rivers, and these rare sightings outside of the historic range suggest some individuals may wander large distances (B. Albanese, pers. comm. August 2018). Starnes (1977) conducted a two-year year study on the closely-related snail darter (Percina tanasi)
Amber Darter SSA Page 5 in the lower Tennessee River and found adult fish moved considerably, especially during the spawning season.
Taxonomy and Description The currently-accepted classification is (Integrated Taxonomic Information System 2018): Kingdom Animalia Phylum Chordata Subphylum Vertebrata Class Teleostei Order Perciformes Family Percidae Genus Percina Species antesella Williams and Etnier, 1977
The amber darter belongs to the subgenus Imostoma, along with the threatened snail darter; the saddleback darter (P. vigil), a widespread fish in the central United States; the stargazing darter (P. uranidea), a species now restricted to the White and Saline systems of Arkansas and Missouri; and the river darter (P. shumardi), a species widespread in Canada and various Gulf drainages (Near 2002). These five species form a monophyletic group. Unlike other Imostoma, male amber darters have a ventral flange at the base of the caudal fin where nuptial tubercles develop (Etnier and Starnes 1993). All Imostoma except the river darter have four or five distinctive dark saddles across the dorsum; the amber darter’s four saddles angle down and forward, with the first saddle located anterior to the spiny dorsal fin (Figure 4) (Williams and Etnier 1977, Etnier and Starnes 1993). All North American freshwater fishes with similar saddles live on rocky substrates, and nearly all occur in flowing water. The saddles likely provide camouflage -- the light spaces between the saddles mimic rocks, and the dark saddles appear as shadows or gaps between rocks. Saddles are spaced unevenly because rocks in streams are a mixture of sizes, and a fish that mimics a series of rocks of similar sizes is more conspicuous than one that mimics different sizes (Armbruster and Page 1996).
The amber darter is small (1.8-3 in long), with a slender body, a moderately long and pointed snout, and eyes located high on the head. The throat area of a breeding male is blue. The venter generally
Figure 4. Amber darters (photos by Brett Albanese, Georgia Department of Natural Resources).
Amber Darter SSA Page 6 is yellow or white, and a distinct bar is present below the eye. The fins are generally clear, with faint dusky markings in the dorsal, caudal, and pectoral fins. The elongate anal fin of breeding males is characteristics of this subgenus.
Natural History
The amber darter occurs in low densities in both the Conasauga and Etowah Rivers, occupying shoals that generally support large populations of other species of small benthic fishes (Freeman and Freeman 1994). Shoals are the shallow sections of rivers, generally with faster-moving water over bedrock, boulder, cobble, and gravel, and typically located on a topographic high in a riverbed. These habitat patches are often widely dispersed; Freeman (1989) counted only 70 shoals, spaced, on average, 0.2-0.56 miles apart depending on section of river, in a 22.5-mile reach of the Conasauga in the heart of the amber darter range. Fish collection data, coupled with nuclear microsatellite analyses (Freeman et al. 2012), suggest amber darters freely disperse between shoals within each river (but not between the two populations).
Amber darters show a preference for moderate water depths (20-50 cm), with deeper depths (>50 cm) used less frequently and shallower waters (<20cm) generally avoided. In spring, riffles and shallow runs are used almost exclusively; deeper run habitats are also utilized in fall (Freeman and Freeman 1994, Golder Associates 1997). In summer, individuals are often found with the aquatic macrophyte, riverweed (Podostemum ceratophyllum) (Freeman 1990) but appear to avoid locations with established Justicia communities
(Golder Associates 1997). Figure 5. Amber darter habitat. The fish requires channel bottoms with moveable The presence of clean substrates and little accumulated silt (photo by Conservation Fisheries, Inc.). Note the moveable gravel (Figure amber darter in the center of the photograph. 5) appears to be most important in determining distribution, likely due to both the fish’s benthic feeding behavior and practice of burrowing into the substrate to seek cover and reduce predation risk (Golder Associates 1997).
Amber darters forage primarily on snails, limpets, and aquatic insects (Etnier and Starnes 1993, Freeman and Freeman 1994). They are visual feeders, foraging during daylight hours by actively
Amber Darter SSA Page 7 searching for prey (Freeman 1990). Freeman (1990) followed 19 individuals each for 30-60 minutes and found they foraged over areas of less than 5 meters square (on average), often moving in roughly circular patterns within the areas. Amber darters often forage together but do not appear territorial or agonistic toward each other or other species, even in shoals with high abundances (Freeman 1988, 1990; Freeman and Freeman 1994).
Individuals likely live four years. Some attain sexual maturity after slightly over one year's growth, and all are mature at two (Etnier and Starnes 1993). Amber darters likely are multiple, promiscuous spawners, as studies of other Percina have indicated (Starnes 1977). Spawning occurs from late fall to early spring (Mettee et al. 1996). Gravid females have been collected as late as April (Etnier and Starnes 1993), and males have been observed flowing milt (seminal fluid) by mid-November, a full 2.5 months before spawning (Starnes 1977). Starnes (1977) suggested that spawning by the closely- related snail darter is determined by an annual hormonal cycle governing sexual maturation, rather than photoperiod or water temperature, and that sexual behavior is triggered by threshold hormone levels after ova have matured sufficiently for deposition. We have no information on the sex ratio of amber darters. Snail darters that Starnes (1977) captured during his two-year study collectively had a male:female sex ratio of 1.1:1.
Amber darters are egg buriers. Freeman (1995) observed nine successful spawning events by captive amber darters. In all events, the female deposited eggs in clean gravel substrate. The eggs were non-adhesive and demersal. Total number of eggs produced during a spawning event is not known, but Starnes (1977) estimated female snail darters lay a maximum 600 mature ova. Eggs produced by captive amber darters hatched 9 days after spawning, and the larvae, when placed in an artificial backwater similar to nursery habitat used by many other fish in the wild, either rested on gravel substrate or in interstitial crevices when not feeding (Freeman 1995). Starnes (1977) hypothesized that larval snail darters were pelagic for 15-20 days and were transported up to several kilometers downstream from the shoal where they hatched. Larvae transform into benthic juveniles around 60 days after hatching and begin to move upstream to suitable shoal habitat. During this time, they likely are highly vulnerable to predation (Starnes 1977). Juvenile amber darters appear in shoals with adults in mid-late summer, after they obtain lengths of around an inch (Freeman and Freeman 1994). By spring, one-year old amber darters have grown to 1.75 inches, and to over 2 inches at 2 years of age (Etnier and Starnes 1993).
The number of amber darters at a given shoal may vary dramatically from year to year (Freeman 1988), and often individuals are not collected in shoals with apparent suitable habitat. During a 1988-1989 survey in the Conasauga River, amber darters were found at 16 of the 28 shoals seined (57%); numbers of individuals at a given shoal ranged from 1-10, and density was estimated at 2.6 individuals per 100 square meters of shoal habitat (Freeman 1989). Numbers of amber darters collected in both river systems, and shoal occupancy in the Conasauga, have declined since the 1988-89 survey (Freeman et al. 2015, 2017). No amber darters were collected in the Conasauga during a 2018 survey of nine shoals in the heart of the species’ range (Bumpers et al. 2019), and only eight individuals were collected in a 2017 survey at eight shoals in the Upper Etowah River.
Amber Darter SSA Page 8
Freeman (1990, 1991) noted that the proportion of young-of-the-year amber darters at a shoal changed over time and suggested that amber darters may be limited primarily by low spawning success or juvenile recruitment, rather than factors affecting adult survivorship. Highly variable reproductive success and/or recruitment at individual shoals, with two to three successive years of poor juvenile recruitment of this short-lived fish, could decimate local amber darter numbers, although year-class failure may be compensated by immigration from nearby shoals (Freeman 1989, 1990). Similar shifts in population age structure among years have been observed for the closely- related saddleback darter in Mississippi’s Homochitto River (Heins and Baker 1989).
One factor in amber darter spawning success and/or recruitment may be extreme flow events (Freeman and Freeman 1994). The timing of floods, in particular, may be a limiting factor. Hagler and Freeman (2014) found evidence of a negative effect of increasing the minimum 10-day moving average in spring, suggesting the amber darter benefits from windows of low spring flow for spawning and recruitment success. High flows may damage eggs, wash larvae from nursery areas, prevent juveniles from migrating upstream to suitable shoal habitat, and increase turbidity and sedimentation that degrades habitat.
Population Needs Both the Conasauga and Etowah amber darter populations need to be able to withstand, or be resilient to, stochastic events and anthropomorphic stressors. Populations need to have a large number of individuals, with adequate numbers of sexually-mature males and females distributed in appropriate sex ratios, across multiple, connected shoals throughout the historic range. Additionally, populations need to exist in locations where environmental conditions provide suitable habitat, water quality, and forage such that adequate numbers of individuals can be supported. Optimally, populations will have sufficient genetic diversity to allow adaptation to changing environmental conditions, including anthropogenic stressors. Without these factors, populations have increased likelihood for localized extirpation.
Species Needs As a species, the amber darter must maintain resilient populations in both the Conasauga and Etowah systems. The breadth of morphological, genetic, and behavioral variation should be preserved to maintain the evolutionary variation of the species, and natural levels of connectivity should be maintained between populations to allow for genetic exchange and recolonization should either population become extirpated.
Amber Darter SSA Page 9 Table 1. Overview of amber darter individual, population, and species needs. Egg/Larvae Flowing water over clean gravel substrate High water quality in shoal and nursery habitat without excess nutrients, added contaminants, or increased turbidity Sexually mature males and females in the shoal Adequate food availability Low spring flows for spawning and recruitment Connectivity to suitable downstream larval nursery habitat
Juveniles Adequate food availability High water quality in dispersal reach without excess nutrients, added contaminants, or increased turbidity that reduces habitat quality, foraging success, adult survival, and recruitment of juveniles into the population. Connectivity to upstream suitable shoal habitat
Adult High quality shoal habitat with minimal siltation or embedded substrate Shoal habitat with areas of moderate water depth flowing over substrate dominated by moveable gravel and small cobble Flow velocity near substrate 0 to -39 cm/sec Average water velocity 10-79 cm/sec High water quality without excess nutrients, added contaminants, or increased turbidity Adequate food availability
Population Sufficient numbers to withstand natural environmental, demographic, and genetic stochastic events Adequate number of occupied shoals, with sexually-mature males and females in adequate numbers and appropriate sex ratios, to provide suitable mates, produce viable offspring, and protect against lean recruitment years Adequate genetic and environmental diversity Sufficient amount of connected habitat within the stream to provide the range of habitat conditions needed to complete the life cycle Habitat connectivity to allow movement of individuals among shoals within each population Continuous flows, with low spring flow to enhance spawning and recruitment success
Species A sufficient number of resilient, connected, diverse populations throughout the historic range
Amber Darter SSA Page 10 CURRENT CONDITION/VIABILITY
Current Population Trends 6.0 73 40 The Georgia Museum of 70 Natural History sampled Number at top of each bar = total shoal fish communities 5.0 number of amber darters collected 57 during surveys. The number of 55 regularly in the Conasauga 54 shoals sampled each year varied. and Etowah River mainstems 4.0 23 in fall 1996-2019 and 1997- 40 2017, respectively, at fixed 3.0 collection stations. In the 31 17
Conasauga, amber darter 2.0 numbers fluctuated during 8 the early study years, but 6 1.0 began to show a declining 7 4 3 7 2 trend in the early 2000’s 0 0 (although 2003 appears to 0.0 96 97 98 99 00 01 02 03 05 06 07 08 12 13 14 16 17 18 19 have been a boom year; Figure 6). By 2012, fewer than Figure 6. Mean number of amber darters collected per shoal in the Conasauga River 1996-2019. Seven to 21 shoals per year were sampled. The 1996-2008 10 amber darters were surveys were conducted in the lower two thirds of the amber darter range, collected during annual between GA Hwy 2 and US Hwy76); surveys 2012-2018 were expanded to surveys, and none were cover the fish’s entire range upstream to TN Hwy 74, a sample reach that included an area Freeman et al. (2015) described as a refuge for amber darters collected in 2018 or 2019 and other imperiled species (data compiled from Golder Associates 2010, (Bumpers et al. 2019, Philip Hagler and Freeman 2012, Freeman et al. 2015, Bumpers and Freeman 2017, Bumpers, University of Bumpers et al. 2019, and Philip Bumpers, University of Georgia, pers. comm., Georgia, pers. comm. October October 2019). 2019). 14 Coosa Chub Coosa Madtom Tricolor Shiner Other species in the 12 Conasauga have shown 10 similar population declines (Figure 7). The Coosa 8 madtom (Noturus sp. cf. N. 6 munitus) has not been collected in the study reach 4 since 1999, and the Coosa chub (Macrhybopsis etnieri) 2 and tricolor shiner 0 (Cyprinella trichroistia) 96 97 98 99 00 01 02 03 05 06 07 08 12 13 14 were not observed 2005- Figure 7. Mean number of individuals collected per shoal for three non-listed, but 2008. These three taxa, plus declining, fish species in the Conasauga. Number and location of shoals sampled, as well as data sources, are identified in Figure 6. the amber darter, represent
Amber Darter SSA Page 11 diverse phylogenies (two cyprinids, one ictalurid, and one percid), feeding behaviors (i.e., water- column and benthic foragers), and spawning modes (i.e., crevice-spawning, broadcast-spawning, nest-guarding, and gravel spawning) (Freeman et al. 2017). The Coosa Madtom has not been detected in the Conasauga downstream of TN Hwy 74 since 2000, but E-DNA analyses suggest the fish may still be present in the system (Bumpers and Freeman 2017).
The amber darter also appears to be utilizing less of its known range in the Conasauga (Figure 8). During 2012-2014 surveys, the fish was found at only a few sampled shoals (and at no survey locations in 2018). It has not been collected in the lower portion of its range, below US Highway 74 near Dalton, Georgia, since 1995 (Hagler and Freeman 2012).
Figure 8. Historic amber darter range in the Conasauga (black circles) vs. recent collections (yellow circles) at 12 survey locations in 2012 and 21 locations in 2013-2014 (figure modified from Hagler and Freeman 2012 and Freeman et al. 2015). No amber darters were collected in the recent 2018 and 2019 surveys (Bumpers et al. 2019, University of Georgia, pers. comm. October 2019).
Amber Darter SSA Page 12 In the Etowah, Bumpers et al. (2018) analyzed fish count data from shoals sampled 1997 to 2017 in the upper two-thirds of the historic amber darter range (Figures 9 and 10; Stations 1-10) to assess fish population trends. The amber darter exhibited the steepest decline of any of the 14 focal species over the survey period. Poisson regression indicated that the expected number of amber darters captured per site, after correcting for differences in flow, effort (e.g., number of kicksets), and other variables, declined from ten individuals in 1997 to only Figure 9. Amber darter sample locations in the Etowah River. Stations 1-10 were sampled 1997-2017. Stations 11-16 were sampled 2007-2014 (CCR three in 2016. The Coosa Environmental 20160. Only one amber darter was located in this lower third of madtom also exhibited sharp the historic range. (Figure from Bumpers and Freeman 2016, modified to include survey locations sampled by CCR Environmental, Inc. 2016). declines in counts, but the Coosa chub and tricolor shiner, which 10 were mostly 89 9 82 Number at top of each bar is the absent over the 78 8 total number of Conasauga logperch same general collected that year 7 time period in the 59 Conasauga, 6 52 54 increased in the 5 42 38 Upper Etowah 4 34 14 26 River. 3 21 2 16 8 The amber darter 1 is less abundant 0 at Stations 7-10 1997 2002 2003 2004 2005 2006 2007 2008 2009 2012 2014 2015 2016 2017 than at upstream Figure 10. Mean number of amber darters collected per shoal in the upper two-thirds of the amber sites (Hagler and darter range in the Etowah River (at Sites 1-10). In most years, 10 shoals were sampled, although high Freeman 2014), water prohibited survey of all shoals in some years (data compiled from Freeman and Barnes 1997, and declining unpublished survey data, Bumpers and Freeman 2016, Bumpers et al. 2018). abundance in a downstream direction appears to continue into the species’ lower range in the Etowah, based on fish collections from Stations 11-16 from 2007 to 2014 (CCR Environmental, Inc. 2016). Only a single amber darter was collected in a 2014 survey at Sites 11-16, and none were
Amber Darter SSA Page 13 found at any of the six sites in 2010. The amber darter’s slow decline in the Upper Etowah over time is concurrent with population increases and urban development in all four Georgia counties that lie within or upstream of Lake Allatoona; from 1970 to 2017, the human population in Lumpkin, Dawson, Forsyth, and Cherokee Counties increased nine-fold, from 60,354 to 532,792 individuals (US Census Bureau 1995, 2012, 2017).
Count data, as depicted in Figures 7 and 10, provide a general overview of fish populations, but they generally are biased because they do not consider capture efficiency, which is the proportion of fishes actually present that are captured during sampling. Capture efficiency may vary among species and over time due to changes in water depth and velocity, turbidity, amount of large woody debris, and other factors that impact observers’ ability to capture fish (Price and Peterson 2010). To avoid this bias, Freeman et al. (2017) used time series analysis to evaluate if occurrence (e.g., species presence vs. absence in shoal) of 26 small-bodied shoal species, like the amber darter, had declined in the Conasauga and Etowah River mainstems over the past 20 years. The issue of incomplete detection was addressed by (1) using data from multiple surveys at a site in a single year to estimate species detection and (2) analyzing survey data using a multispecies framework that allowed inferences about dynamics for a suite of species assumed to respond similarly to environmental change. Their evaluation indicated that (1) occurrence of the amber darter became less common at the Conasauga sample sites, and (2) overall, species richness in the Conasauga, in the heart of the amber darter range between Georgia Highway 2 and US Highway 76, declined over time from a mean of 22.9 to 19.4 species. In the Etowah River, in contrast, there were no apparent declines in shoal occupancy at Sites 1-10 for any of the 28 species included in the analysis, including amber darters (Sites 11-16 were not included in the analysis). Persistence and colonization probabilities varied over time at the ten Etowah sites for these species but did not display a temporal trend (Freeman et al. 2017).
Current Species Viability
Amber Darter Resiliency (Current Conditions): Resiliency (measured at the population level) is the foundational building block of the SSA Framework. For the amber darter to be viable, some proportion of the populations must be resilient enough to withstand stochastic events and anthropomorphic stressors. For this resiliency assessment, we considered individuals in the two rivers to be separate populations, isolated from each other by Lake Allatoona on the Etowah River. We are unable to divide these two populations into smaller management units; the fish have pelagic larvae that migrate upstream as juveniles, and adults appear to move freely among shoals within each river system (Freeman et al. 2012). Individuals that may occur in Sharp Mountain Creek, Shoal Creek, or other Upper Etowah tributaries were considered part of the larger Etowah River population. The Coosawattee River, where a single amber darter was collected in 2010, was not included in this assessment. We have no data suggesting a permanent population currently or historically in this river. The current condition of the Conasauga and Etowah populations was assessed based on population and habitat factors outlined in Table 2.
Amber Darter SSA Page 14 Table 2. Population characteristics used to create condition categories in Table 3. Condition Annual Abundance Change over 20 Years Historic Range Occupancy High Stable or increasing Well distributed Moderate 1-5% decline Reduced use within historic range Low 5-10% decline Absent from 25% of historic range Very Low >10% decline Absent from 50% of historic range
Multivariate autoregressive state-space (MARSS) analysis, which provide estimates of long-term population growth rates, estimated that amber darters had declined approximately 12% annually in the Conasauga and 9% annually in the Etowah River over the past two decades (Stowe et al. 2019). University of Georgia and USGS personnel are developing viability models for the fish – preliminary results suggest that, at current rates of decline, amber darters would be effectively undetectable (defined as a catch-per-unit-effort of 1 fish in 400 seine-sets at a given shoal by experienced field biologists) between 2021 and 2032 in the Conasauga and 2030 and 2047 in the Etowah (Edward Sage Stowe, UGA, and Mary Freeman, USGS, pers. comm., November 2018). Shoal occupancy has declined in the Conasauga, and fish in both systems have been extirpated or greatly reduced in abundance in downstream reaches within the historic range. The causes of these declines have not specifically been identified, and may be contaminants, elevated nutrients, altered hydrology, warming temperatures, disease, or a combination of these factors or other unidentified factors. Amber darter resiliency in the Conasauga and Etowah basins is very low and low respectively (Table 3).
Table 3. Amber darter current conditions (resiliency). Population Annual Abundance Change over 20 Years1 Historic Range Occupancy 12% 50% Conasauga Very low Very low 9% Only 1 fish found in lower third of range Etowah during last 2 surveys Low Low 1 Based on MARSS analysis (Stowe et al. 2019).
Amber Darter Representation: Multiple resilient populations contribute to the range of variation found in a species; the more variable a species is, the greater the adaptive diversity and the ability of a species to adapt to changes in the environment. Maintaining adaptive diversity includes conserving the genetic diversity of a species. Freeman et al. (2012) analyzed amber darter genetic samples using mitochondrial DNA sequencing of two genes (Cytb and ND2) and six polymorphic microsatellite loci. Clips were collected from caudal fins of 363 amber darters from the Conasauga and Etowah Rivers. A fin clip from the individual collected in the Coosawattee River in 2010 also was analyzed.
Mitochondrial DNA Sequencing: Mitochondrial DNA (mtDNA) is useful for determining the relationships between closely-related groups. It is inherited, generally, from mother to offspring. Nineteen individuals from the Conasauga and Etowah Rivers were screened for
Amber Darter SSA Page 15 DNA sequence polymorphism. Overall, only 10 unique haplotypes were seen, and the most divergent haplotypes (found in two individuals from the Etowah) differed by only 11 base pairs (0.5%). Compared to similar studies of other southeastern freshwater fishes, the amount of mtDNA variation seen in amber darter is very low (Dakin et al. 2008). Sequencing the MtDNA cytochrome b gene showed very low levels of variation and no phylogeographic structure in amber darters throughout the Conasauga and Etowah Rivers in Georgia. These results likely are due to recent divergence or separation of the two populations. The presence of anthropogenic barriers to fish dispersal (especially Allatoona Dam, which was impounded in 1950) precludes natural movement of amber darters between the Conasauga and Etowah populations, but, prior to barrier construction, amber darters possibly existed continuously through the Conasauga, Oostanaula, and Etowah Rivers (Freeman et al. 2012).
Microsatellites: Microsatellites are short tandem repeats, or units of repeating DNA sequences, that have relatively high mutational rates and accumulate differences between isolated populations more quickly than the slower-mutating mitochondrial sequences. Microsatellites are applied in population genetics to measure levels of relatedness between subspecies, groups and individuals and are especially useful for phylogeographic studies because they are nuclear markers (as opposed to the maternally-inherited mitochondrial genes) and reflect both male and female patterns of movement (Dakin et al. 2008).
Freeman et al. (2012), found high levels of genetic diversity within and between the Conasauga and Etowah River amber darter populations at the six nuclear microsatellite loci. We do not know if the diversity measured at the microsatellite markers is proportional to that at underlying loci that express traits important for survival. Little microsatellite differentiation existed between shoals within either population, suggesting free dispersal of amber darters between shoals within each population (but not between populations). Diversity was lower in the Etowah River than the Conasauga, despite the fact that more than twice as many individuals were collected in the Etowah. The most likely explanation for this reduced diversity is a recent bottleneck in the Etowah’s population size (Freeman et al. 2012), which tallies with survey data from the 1980’s (see page 4). A bottleneck occurs when a natural or anthropogenic disaster reduces the size of a population, leaving fewer individuals that do not represent the total genetic makeup of the initial population. The effects can vary depending on both the size to which the population is reduced and the duration of the bottleneck (i.e., the number of generations).
Current Redundancy: A species needs to have multiple, resilient populations, distributed throughout its range, to withstand catastrophic events, such as chemical spills, wildfire, hurricanes, droughts, and other events that might decimate one or more populations. Those populations need to have connectivity to facilitate gene flow and allow emigration from source to sink areas. The amber darter has two small, declining populations effectively isolated by Lake Allatoona, a 12,000-acre U.S. Army Corps of Engineers reservoir. MARSS analyses documented
Amber Darter SSA Page 16 that amber darter population fluctuations in the Etowah and Conasauga covaried, suggesting that the two populations experience correlated environmental variation (Stowe et al. 2019).
Translocation and/or a captive propagation and release program could increase the likelihood that both populations persist, but, given the small populations from which stock would be collected, and the lower genetic diversity in the Etowah, either method may increase the potential for founder effect. The founder effect is a special case of genetic drift, occurring when a small group in a population splinters off from the original population and forms a new one. The new population may have less genetic variation than the original population and may be distinctively different, both genotypically and phenotypically, from the parent population.
Summary: The amber darter lacks resiliency and redundancy, and, although genetic diversity (as represented by microsatellite markers) is relatively high, the declining populations in both rivers suggest the species, as a whole, does not have the capability to adapt to stochastic events and/or to current anthropogenic-related habitat degradation.
Amber Darter SSA Page 17 FACTORS INFLUENCING VIABILITY
Small Populations and Limited Geographic Range Narrow endemic species with small populations and limited geographical ranges, like the amber darter, are vulnerable to extinction (Moyle and Williams 1990), with environmental, demographic, and genetic stochastic processes playing a critical role in their vulnerability (Purvis et al. 2000). Theory suggests that fitness and genetic diversity decrease when populations become small, and that this deterioration precipitates positive feedback loops called extinction vortices. Gilpin and Soule (1986) were the first to conceptualize this process, describing how demographic, environmental, and genetic stochasticity could interact with each other and with deterministic factors, such as habitat loss, to mutually reinforce and accelerate loss of small populations. In an analysis of 10 wildlife populations that went extinct, Fagan and Holmes (2006) found that all exhibited dynamics indicative of an extinction vortex before collapse.
Breeding opportunities may be reduced in a small population, particularly when it is dispersed (like the amber darter, among widely-separated shoals), because there is less probability that individuals of the opposite sex will meet to breed. Small and isolated populations also are more vulnerable to demographic stochasticity (chance independent events of individual mortality and reproduction, causing random fluctuations in population growth rate) and environmental variation (temporal fluctuations in mortality and reproductive rates of all individuals in a population in the same or similar fashion, causing population growth rate to fluctuate randomly in populations of all sizes) than large populations (Keller and Waller 2002). For species with small ranges, vulnerability is exacerbated by the threat of catastrophic events (natural or anthropogenic) that can significantly reduce or extirpate a population (Angermeier 1995).
If populations remain small and isolated for multiple generations, they face two genetic threats -- genetic drift and inbreeding depression (Soule and Mills 1998, Keller and Waller 2002). Genetic drift is the random change in allele frequency that occurs because gametes transmitted from one generation to the next carry only a sample of the alleles present in the parental generation. Genetic drift decreases variation within populations (loss of heterozygosity and eventual fixation of alleles) -- every population experiences genetic drift, but the effects become more pronounced as population size decreases or in a population that undergoes occasional fluctuations to small population size (e.g., bottlenecks or founder/colonization events). In the latter case, allelic variation is likely to decrease, but heterozygosity often remains relatively unchanged as long as the population rebounds rapidly (summarized from Ellstrand and Elam 1993). Inbreeding is the mating of related individuals and will most likely occur when populations are small or when they exhibit spatial genetic structure (Ellstrand and Elam 1993). The net result is loss of genetic variation that may (1) decrease the potential for a species to persist in the face of abiotic and biotic environmental change and (2) alter a population’s ability to cope with anthropogenic threats.
Anthropomorphic Stressors: Multiple stressors associated with historic and current land use influence amber darter viability:
Amber Darter SSA Page 18
Historic Land Use: Harding et al. (1998) emphasized the influence of the “ghost of land use past” on the present-day diversity of stream invertebrates and fish. In comparing diversity in streams that drained agricultural vs. forested land, they determined that long-term agricultural disturbances can limit recovery of stream diversity for decades, even well after the land reforests. Wenger et al. (2008) evaluated three indicators of historic vs. current land use in predicting fish occurrence – for four of five Etowah River fish species (including a surrogate for the amber darter), the best-supported models were those that included both historic land use and current effective impervious cover predictor variables.
The Conasauga and Etowah Rivers originate in the Blue Ridge Province, which was heavily timbered from the late 19th century through 1930 (Walker 1991, as cited in Walters 1997), and, by 1908, an estimated 86% of timberland in the Blue Ridge had been cut (Yarnell 1995, as cited in Edwards et al. 2013). Timber harvest can influence stream flows by increasing total discharge, altering peak discharge rates, and changing the duration of high and low flows. These changes alter the energy and sediment-transport capability of the system and can alter both channel morphology and aquatic habitat (Troendle and Olsen 1993). Many watersheds in the eastern U.S. responded to rapid deforestation of both slopes and valley bottoms with a common suite of changes over time, including (summarized in Miller et al. 2015):
1. Increased runoff and runoff rates to downstream reaches. 2. Subsequent hillslope gullying and accelerated soil erosion, which increased sediment deposits in downstream channels and floodplains (legacy sediment). 3. After timber harvest (in many instances), a period of reforestation and/or application of improved watershed management practices that reduced runoff and sediment loading. 4. Subsequent channel incision as sediment loads decreased, with increasing lack of connectivity to the original floodplain, which remained elevated with legacy sediment.
In the Etowah Basin, and to a lesser degree in the Conasauga, widespread construction of lowhead mill dams up until the early 1900’s had similar impact to timber harvest on stream channels. Sediment gradually filled these reservoirs, but many dams were breached when the facility no longer was needed, and the channel incised through the collected sediments (Walter and Merrits 2008). The current condition of a channel that has undergone sediment loading/incision, may depend on where the watershed rests along a disturbance-recovery sequence. Channel evolution models suggest many incised streams eventually widen and aggrade, forming a new, narrow floodplain within the incised channel, before reaching a quasi- equilibrium status with either (1) a single channel with an abandoned floodplain terrace and a newly-formed, narrower floodplain at a lower elevation (Simon and Hupp 1986) or (2) a multi- anastomosing channel network connected to a frequently-inundated floodplain (Cleur and Thorne 2013), depending on whether the pre-settlement stream condition was a sinuous single channel with riffle-pool complexes or a swampy shrub-scrub meadow with shallow anabranching streams (Walter and Merrits 2008).
Amber Darter SSA Page 19 Trimble (1974) timed erosive land use associated with European settlement in the Etowah Basin (Southern Piedmont Province) to a period beginning before 1860, increasing in intensity through at least 1920, and abating to low intensity by 1967 (Figure 11), and it is likely that the progression had a similar timetable in the Conasauga Basin (Ridge and Valley Province). Jackson et al. (2005) in a study of Murder Creek in Georgia’s Piedmont, found historical row- crop agriculture led to Figure 11. Timing of erosive land use in the Southern Piedmont (figure from floodplain deposition of a Trimble 1974). The general location of the amber darter range in the Etowah Basin is marked with the red circle in the top left diagram. nearly-uniform 5.3 feet of sediment, largely a legacy of poor farming practices in the late 1800s and early 1900s -- floodplain accretion rates and streambank conditions suggest streams had been in a state of net sediment export over the previous 50 years (e.g., legacy sediment, as measured in downstream Lake Sinclair, which was constructed 1947-1953). Jackson et al. (2005) observed that most of the streambanks in their study area were steep and unstable. Low order streams were highly incised; larger order streams were not as consistently incised but still possessed steep and eroding streambanks. Everywhere except in shoal areas, channel beds were composed of loose and highly mobile sands. Vegetated bars were forming in some streams, and floodplain surfaces showed no consistent signs of elevation change over the last 50 years. Jackson et al. (2005) concluded that these conditions were consistent with a stream system that was eroding valley sediments after a period of high sediment input and valley aggradation.
Current Land Use in the Upper Conasauga Basin: Although uplands adjacent to some mainstem reaches and tributaries are urbanizing, particularly in the Mill Creek – Tennessee and Sumac Creek basins, most continue to have support agriculture in the floodplain (Table 4), where the land is flat, has poor drainage, and is prone to flooding. Cattle and hay remain important agricultural products, although production of cotton and corn has declined significantly. But the major changes in agricultural crop production during the period when recent surveys documented declines in fishes are (Cindy Askew, NRCS, pers. comm., June 2008):
Amber Darter SSA Page 20 • A transition towards large-scale poultry production (Table 4). • Subsequent widespread use of poultry litter as a fertilizer for pastureland or row crops. A switch to use of Roundup® Ready® seed, which altered timing and application amounts of the herbicide glyphosate and “inert” ingredients in formulations.
Table 4. Changes in agricultural land use and production in Murray and Whitfield Counties, Georgia, 1934-2017 (data compiled from USDA 1935, 1992, 2012, 2017). Note the significant decrease in farmland from 1935 to 1992, the loss of cotton, corn, and most grains as commodity crops, and the sharp increase in poultry production after 1992. Murray County, Georgia Whitfield County, Georgia Change 347 sq. mi. (218,880 acres) 291 sq. mi. (181,120 acres) 1935 to 1934 1992 2012 2017 1934 1992 2012 2017 2017 #Farms 1,581 216 320 278 2031 395 378 386 -2,948 % in Farmland 65.5 15.0 21.5 21.6 87.8 21.4 21.6 20.2 -44-67% #A in Farmland1 143,446 32,950 46,960 47,189 158,995 38,691 39,107 36,552 -218,700 #A Harvested2 33,409 7,780 17,289 9,242 41,981 8,303 9,303 7,327 -58,821
#Head Cattle/Calf No data 5,944 6,783 8,839 No data 10,334 7,729 11,677 No data #Broilers Sold3 85,824 4,962,000 22,093,420 35,002,026 58,922 11,326,783 28,315,999 21,725,500 +55,280,060
#A Corn 16,079 1,816 4,270 748 20,274 1,135 876 325 -35,280 #A Wheat 717 721 (D)4 (D)4 475 0 90 (D)4 Gone #A Oats/Rye 727 0 0 218 0 0 Gone #A Cotton 9,719 0 0 0 10,860 0 0 0 Gone #A Soybean No data 1,868 6,033 1,332 No data 444 240 (D)4 No data #A Irish Potatoes 162 0 0 247 6 1 Gone #A Sweet Potatoes 212 0 0 373 0 0 Gone #A Forage/Hay 6,338 3,549 6,355 6,567 9,308 6,194 8,066 6,851 -2,228 1 Lands used for crops, pasture, or grazing, plus woodland and wasteland that is part of the total operation. 2 Land from which crops were harvested and hay cut. 3 1934 numbers include layer inventory. 4 USDA withheld data to avoid disclosing information about individual farms
Agricultural ditches are prominent in fields along the river’s mainstem and some tributaries (Figure 12). The Nature Conservancy located hundreds of ditches in a 2008 survey of a 40- mile reach of the upper and middle Conasauga (Katie Owens, TNC, pers. comm., Feb. 2009). These man-made networks are efficient at draining croplands but (1) tend to bypass agricultural best management practices, conveying polluted runoff directly into streams, and (2) alter hydrology in the river by altering volume and timing of runoff. These alterations, in turn, drive a complex of changes in stream Figure 12. Drainage ditches, some dozens of feet wide, convey pollutants in stormwater runoff directly into the morphology, instream and riparian habitats, Conasauga. nutrient cycles, turbidity and sedimentation that affects aquatic biota (Figure 8, Blann et al. 2009).
Amber Darter SSA Page 21
Figure 13. Effects of agricultural drainage on aquatic ecosystems (from Blann et al. 2009). Tributaries entering the Conasauga downstream of the National Forests drain landscapes with more agriculture, urban development (particularly in the Mill Creek-Tennessee and Sumac Creek basins), and other land disturbance than in the forested headwaters, and these tributary inputs influence water quality in the mainstem. Even as early as 1995, water clarity visibly declined downstream from the TN Hwy 74 bridge crossing, with significant degradation of water quality within the first few miles downstream of the Tennessee-Georgia border (Freeman 1995). Baker et al. (2013), during studies conducted 2011-2012, found nitrogen was a limiting factor for primary production at sites within the national forests downstream to the US Hwy 411 crossing; nitrogen and phosphorus both were limiting at Easley Ford in 2012, but there was no limitation for either nutrient just a few miles downstream at the TN Hwy 74 and GA Hwy 2 crossings. Extensive mats of benthic algae were observed in 2000 and 2001 along a 28-mile reach of the Conasauga from TN Hwy 74 downstream past Tibbs Bridge (Freeman and Wenger 2001, Freeman et al. 2007), a reach that includes much of the amber darter’s range. Studies in the Conasauga mainstem over the past 20+ years have documented a decline in Podostemum and an increase in algal and diatom mat occurrence, from upstream to downstream along the mainstem (Freeman and Freeman 2019), concurrent with increases in water turbidity from less than 2 NTUs in the upstream national forest to greater than 10 NTUs in downstream reaches (Argentina et al. 2010), even during periods of limited runoff.
Amber Darter SSA Page 22 Current Land Use in the Upper Etowah River Basin: Agriculture comprises less than 15% of land use in the Upper Etowah Basin, a significant decline from 1935, when almost 85% of Cherokee County (231.7K of 277.8K acres) and 39-60% of Dawson and Lumpkin Counties were in agricultural use (Table 5). A large percentage of the agricultural lands that are harvested are in pasture, rather than row-crop production. Poultry production significantly increased basin-wide, compared to 1935, except in the urbanizing Cherokee County.
Table 5. Changes in agricultural land use and production in counties of the Upper Etowah River watershed, Georgia, 1934-2012 (data compiled from USDA 1935, 1992, 2017). Data for Forsyth County were not analyzed because little of the county lies within the Etowah watershed. Amber darters do not occur in Lumpkin County, but land use in this upstream county can influence downstream water quality. Cherokee County, Georgia Dawson County, Georgia Lumpkin County, Georgia Agriculture Type 434 sq. mi. (274,560 acres) 214 sq. mi. (138,240 acres) 284 sq. mi. (179,200 acres) 1934 1992 2017 1934 1992 2017 1934 1992 2017 #Farms 2,530 473 430 729 170 192 865 229 240 % in Farmland 84.4 12.2 9.7 60.3 13.8 13.7 39.0 13.0 15.0 #A in Farmland1 231,746 33,641 24,034 83,406 19,060 18,950 69,943 23,284 26,960 #A Harvested2 52,209 3,466 5,051 15,619 2,293 2,466 13,096 2,938 5,309
#Head Cattle/Calves No data 9,196 3,957 No data 5,538 2,848 No data 5,211 4,979 #Broilers Sold3 128,536 19,413,648 2,068,065 25,753 13,658,034 13,679,050 30,000 12,670,517 8,395,650
#A Corn 25,390 71 158 9,993 664 262 842 673 721 #A Wheat 1,680 (D)4 0 676 0 0 264 (D) (D) #A Oats/Rye 782 0 479 0 252 0 #A Cotton 16,089 0 0 2,962 0 0 1,566 0 0 #A Potatoes 698 (D) 221 4 382 0 #A Forage/Hay 4,683 2,797 4,296 804 1,152 2,061 829 1,849 4,343 1 Lands used for crops, pasture, or grazing, plus woodland and wasteland that is part of the total operation. 2 Land from which crops were harvested and hay cut. 3 1934 numbers include layer inventory. 4 USDA withheld data to avoid disclosing information about individual farms
The Etowah lies on the north edge of the Atlanta metropolitan area and experienced rapid urban growth before the December 2007-June 2009 Great Recession. The suburban counties that comprise the lower portion of the Etowah basin were among the fastest growing counties in the US (Table 6). Growth sputtered for a few years after the recession, but, by 2017, the Atlanta-Sandy Springs- Roswell area was the ninth largest and third fastest-growing metro-area in the nation, with annual addition of over 89,000 citizens (U.S. Census Bureau 2018). By 2030, the most rapid growth is anticipated to shift outward to encompass a ring of counties further from the center of Atlanta (Figure 14), with a projected 2.9-3.9% average annual population increase in all three counties in the Etowah Basin where amber darters occur (Georgia Office of Planning and Budget 2010).
Amber Darter SSA Page 23 Table 6. Population growth 1970-2017 and anticipated growth to 2050 in the Upper Etowah River Basin, Georgia (US Census Bureau 1995, 2012, 2017; Georgia Office of Planning and Budget 2010, 2018). Amber darters only occur in the counties shaded yellow, but activities in the more upstream Lumpkin County can influence downstream water quality. Statistic Lumpkin Dawson Forsyth Cherokee Population 1970 8,728 3,639 16,928 31,059 Population 1990 14,573 9,429 44,083 90,204 Population 2010 29,966 22,330 175,511 214,346 Population 2017 32,873 24,379 227,967 247,573 Population 2030 (estimated) 37,267 45,368 372,952 415,826 Population 2050 (estimated) 44,201 40,003 597,255 494,713 Upstream> > > > > > > > > > > > > > > > > > >Downstream
Figure 14. Average annual population change projected in Georgia 2010-2030. Areas where future urban development may impact downstream amber darter habitat are circled in yellow (Etowah basin) and orange (Conasauga basin) (figure modified from Georgia Office of Planning and Budget 2010).
Amber Darter SSA Page 24 Stressors in the Conasauga and Etowah Basins: Likely stressors on amber darters associated with historic and current land use include fine sediment (including legacy sediment), excess nutrients/cultural eutrophication, increased impervious surface, glyphosate-based herbicides, lack/loss of riparian buffers, reduction in habitat diversity due to loss of Podostemum, and impoundments. Climate change likely is a region-wide stressor (Table 7).
Table 7. Likely anthropomorphic stressors for amber darters. Stressor Conasauga Etowah Fine sediment (legacy, agricultural, development) Yes Yes Excess nutrients (fertilizer, human/animal waste) Yes Less than in Conasauga Increased impervious surface (urbanization) Likely increase in future Yes Glyphosate-based herbicides Yes No Lack/loss of riparian buffers Yes Less than in Conasauga Reduction in habitat diversity due to loss of Podostemum Yes No Reservoirs and dams, particularly Lake Allatoona No Yes Climate change Yes Yes
Fine Sediment (e.g., sand, silt, and clay): The detrimental effects of sediment on aquatic communities have been widely demonstrated and include (1) habitat degradation, (2) reduced productivity that affects the food chain, (3) lethal effects that kill individual fish, cause population reductions, or damage the capacity of the ecosystem to produce fish, (4) sub-lethal effects that injure the tissues or physiology of the organism but are not severe enough to cause death, and (5) behavioral effects that change activity patterns or alter the kinds of activity usually associated with an organism in an unperturbed environment (Newcombe and McDonald 1991, Wood and Armitage 1997). Specifically: • Fine sediments in the water column increase turbidity, limit light penetration, transport sorbed contaminants, and potentially reduce primary productivity that affects the food chain (Davies-Colley and Smith 2001). Lloyd et al. (1987) suggested that a turbidity of only 5 NTU from alluvial mining in Alaska could decrease the primary productivity of shallow clear-water streams by 3-13%, while an increase of 25 NTUs could cause a 13-50% productivity decrease in shallow streams. Van Nieuwenhuyse and LaPerriere (1986) found a 170 NTU turbidity caused a 50% reduction in primary production, while a 1200 NTU resulted in no primary productivity. • Deposited silt and sediment can entomb and smother the stream bottom, filling interstices between cobble and gravel particles. This can alter the periphyton and macroinvertebrate communities (Puglsey and Hynes 1983, Soroka and MacKenzie-Grieve 1983, Newcombe and Jensen 1996) and bury fish eggs, larval nurseries, and adult foraging and resting habitat. Walters et al. (2003a) described how sediment delivery and deposition in the Etowah River basin resulted in homogenized fish assemblages by creating turbid streams and embedded channel beds. Berkman and Rabeni (1987), in a study of Missouri streams, noted that that, as siltation increased, abundance of two fish feeding guilds - benthic insectivores (like the amber darter) and herbivores - was reduced as the percent of fine substrate increased. Community dominance changed from riffle-specific species to ubiquitous and run-specific species.
Amber Darter SSA Page 25 • Benthic food organisms may be smothered by silt, reducing food biomasss and making items harder for visually-feeding fish to locate (Ryan 1991). • Suspended sediment can reduce spawning success. Studies have shown that increased levels of suspended sediment reduced success of both salmonids and minnows, many of which depend on clear water for visual reproductive cues (Burkhead and Jelks 2001). • Silt may have direct lethal effects on fish by clogging gillrakers and gill filaments (Bruton 1985, Newcombe and Jensen 1996). Acceptable levels may depend on the nature and concentration of the silt, water oxygenation and temperature, species and size of the fish, and concentration of suspended sediment to which it has become acclimated (Ryan 1991).
Excess Nutrients/Cultural Eutrophication: Nutrients, especially nitrogen and phosphorus, are essential for plant and animal growth, but excessive application and subsequent runoff into receiving waters, particularly at times when sensitive early-lifestages of many fish and aquatic invertebrates are present, can cause both eutrophication of aquatic systems and adverse impacts to aquatic communities. The chief effect of eutrophication is the stimulation of algal growth and shifts in the algal community, which can reduce water clarity and degrade water quality. Extensive algal blooms can can smother Podostemum and alter habitat by covering gravel substrates where fishes forage and deposit eggs (Freeman et al. 2017). Algal blooms limit light penetration, reducing growth, causing die-offs of plants in littoral zones, and lowering the success of predators that need light to pursue and catch prey (Lehtiniemi et al. 2005). High rates of photosynthesis associated with eutrophication can deplete dissolved inorganic carbon and raise pH to extreme levels during the day. When dense algal blooms eventually die, microbial decomposition severely depletes dissolved oxygen, creating hypoxic or anoxic ‘dead zones' lacking sufficient oxygen to support most organisms. This can lead to fish kills, as well as more subtle changes in ecological structure and function, such as lowered biotic diversity and reduced recruitment in fish populations. Hypoxia and anoxia are more likely to occur in summer, when the solubility of oxygen decreases and oxygen demand (respiration rate) generally increases as temperature increases (National Academy of Science 2000).
Increases in nutrient loads can stimulate the proliferation of pathogens that adversely impact fish and mussel species (Coyner et al. 2003). Smaller streams depend on annual leaf fall to support biological diversity and productivity (Wallace et al. 1997), and inputs of nitrogen and phosphorus to surface waters may accelerate decomposition of leaf packs by 50%, disrupting annual carbon usage patterns and food web functions (Rosemond et al. 2015). Nitrate has also been implicated as an endocrine-disrupting chemical due to its potential to be converted to nitric oxide, which can modify steroidogenesis in aquatic animals (Hamlin et al. 2008).
Nitrogen cycles rapidly among ammonium (NH4), ammonia (NH3), nitrate (NO3), nitrite (NO2), atmospheric nitrogen (N2) and organic nitrogen (i.e., N bound in the biomass of organisms), plus intermediate forms. Ammonium and nitrate are the forms most rapidly taken up by plants. Denitrification converts nitrate to atmospheric nitrogen, providing a mechanism for removal from the system. Water quality studies conducted 1997-2012 in the Conasauga documented both
Amber Darter SSA Page 26 (1) an increasing trend in NO2+NO3 concentrations in a downstream direction and (2) comparatively higher concentrations of total nitrogen (around threefold) in 2011-2012 samples vs 1997-2000 samples (Hagler and Freeman 2012). Local spikes with very high concentrations of NO2+NO3 were measured at multiple sites in the Middle Conasauga mainstem 1997-2007, including a November 1998 sample with a concentration of 44.46 mg/l NO3+NO2 at Hwy 286 -- this value far exceeds the EPA’s Maximum Contaminant Level Goals of 10mg/l NO3 and 1 mg/l for NO2 safe drinking water standard (Freeman et al. 2007). From 2012-2013, Lasier et al. (2016) found nutrient enrichment of Conasauga surface waters was widespread, with concentrations of NO3 and phosphorus exceeding levels associated with eutrophication. NO3 was measured in surface waters from each of 15 sites, and phosphorus was common at all but the two most upstream sites (both in Tennessee), with both elements often exceeding harmful concentrations.
Freeman and Wenger (2001) reported a large bloom of benthic algae in October 2000 that spanned almost 30 miles of high-quality shoal habitat from near the Tennessee Hwy 74 crossing to downstream of Tibbs Bridge. The bloom was evident below the Mill Creek (TN) and Perry Creek (GA) confluences, the first tributaries that drain watersheds with larger amounts of agricultural lands. The blooms occurred in shallow water (0.75m or less) along shoals; mats of algae covered Podostemum, and fishes were present in lower abundances in the areas with algal mats (Freeman et al. 2007). The same phenomenon was observed the following year, in October of 2001 and in years since, to a lesser extent (Freeman et al. 2007). Currently, water clarity is significantly reduced in the lower half of the amber darter’s range, where the fish is now collected rarely, likely due to high concentrations of diatoms and other algae (Freeman and Freeman 2019) that may affect foraging and spawning success (Mary Freeman, USGS, pers. comm., November 2018).
The Etowah River and several tributaries have nutrient levels elevated relative to EPA guidelines. Although nutrient concentrations do not appear to be increasing, it is likely that elevated nutrient concentrations negatively impact the basin (Bumpers and Freeman 2016).
Likely sources of nutrients in these rivers include: • Agricultural fertilizers: In the Conasauga, there is widespread use of poultry litter as a fertilizer for pastureland or row crops (Cindy Askew, NRCS, pers. comm., June 2008). Poultry litter is a mixture of manure, feathers, spilled food, and bedding material. Surface spreading of litter on agricultural fields allows runoff from heavy rains to carry nitrogen, phosphorus, and other chemicals from manure into nearby streams. Poultry litter has high relative concentrations of nitrogen, with an N:P ratio of 2:1 (Pierson et al. 2001). Since most crops and pasture grasses require an N:P ratio of 8:1, applying sufficient poultry litter to supply the nitrogen needs of crops and pasture will result in excess phosphorus application (Sharpley 1999, Sharpley et al. 2004). Phosphorus will bind to soil and is mobilized with sediment particles after heavy rains, and relatively high phosphorus concentrations have been measured in surface runoff for months following poultry litter application (Pierson et
Amber Darter SSA Page 27 al. 2001). Litter can contain arsenic, which is formed from a chemical routinely used as a feed additive to prevent disease and stimulate growth (Mangalgiri et al. 2015). Other substances often found in poultry litter include fecal coliforms and other pathogens, other heavy metals, pesticides and larvicides used to control flies and litter beetles, estrogens and other hormones, and excess carbon, which can deplete dissolved oxygen in surface waters (Moore 1997). • Urban and suburban development, including lawn fertilizer, discharges or leaks from wastewater treatment plants, and poorly-maintained and/or sited septic tanks. • Atmospheric nitrogen that is fixed by plants, through lightening, or other processes.
Increased Impervious Surface Associated with Urbanization: An urban area is defined as the entire landscape developed for residential, commercial, industrial, and transportation purposes, including cities, towns, suburbs, and exurban sprawl that has a density of >1 residential unit/2 ha (Wenger et al. 2009). A more detailed evaluation of the impacts of urban development of rare fishes in the Etowah Basin is provided in Wenger and Freeman (2007). Urbanization in anticipated to continue throughout the Etowah River basin through 2060, but should be more limited in the Conasauga except, potentially in Mill Creek, which drains the City of Cleveland, Tennessee, and Sumac Creek, Georgia, which drains Cohutta Springs and the new Georgia Ports Authority inland port north of Crandell.
Many studies have demonstrated that fish assemblages respond to a gradient of urbanization, with sensitive fishes disappearing as urbanization increases (Klein 1979, Wang et al. 2000, 2001, Walters et al. 2003b, Roy et al. 2005, Walters et al. 2005). The conversion of a forested or agricultural landscape into parking lots, buildings, and lawns produces a cascade of impacts to stream Figure 15. Impervious surfaces alter the hydrologic cycle (figure from systems, including https://www.bluespringsgov.com/1051/How-Urbanization-Affects-the-Water- changes to hydrology,
Amber Darter SSA Page 28 geomorphology, water temperature, and stream chemistry (Paul and Meyer 2001). Urbanization alters the way rain is conveyed to stream channels (Figure 15). In a vegetated ecosystem, some precipitation evaporates, returning to the atmosphere; some infiltrates into the ground; and the remainder becomes surface runoff, traveling via natural channels and man-made drainage systems to larger streams. The volume of evaporation vs. infiltration vs. runoff is governed primarily by the land’s slope, vegetative cover, and infiltration capacity of the underlying soil (sand > clay> bedrock). Impervious and reduced-pervious surfaces associated with urbanization, such as parking lots, roads, building roofs, and even lawns and playgrounds, alter the natural cycling of water in regions where infiltration and subsurface flow play major roles in the water cycle. The general result is a decrease in the volume of water that evaporates or percolates into the ground and an increase in volume of surface runoff entering stream systems (Booth 1991).
Low impact development is an approach to site development and stormwater management that aims to mitigate the impacts of surface runoff to water bodies by reducing impervious surface and treating runoff using a treatment train of best management practices (BMPs), such as rain gardens, green roofs, swales, and permeable paving. Effective impervious area (EIA) is the portion of the total impervious surface that is hydraulically-connected to a storm sewer system via stormwater drainage pipes, ditches, or other conveyance methods, without any stormwater BMPs to reduce or infiltrate flows or improve water quality.
Changes to channel morphology are among the most common and visible effects of urban development and increased EIA on natural stream systems, particularly in channel reaches that are alluvial (Booth and Henshaw 2001). Leopold (1968), in a study of eastern US streams, found that urban channels tended “to have unstable and unvegetated banks, scoured or muddy channel beds, and unusual debris accumulation.” And Booth (1991) described suburban streams as having a characteristic look: “Their beds are uniform, with few pools or developed riffles… Channel banks are raw and near-vertical, with incisions of one to many feet. The erosion of adjacent steep banks is constantly adding new sediment. Woody debris is small and sparse…. Finally, the aquatic organisms that thickly populate equivalent drainages in undeveloped settings are nearly absent.”
While the effects of urbanization on stream biota are mediated by a variety of factors (including hydrology, previous land use, soil type, water quality, geomorphology, temperature, and stream flow), changes in urban streams have been so consistently observed, worldwide, that scientists have a term for the ecological degradation - urban stream syndrome. Common, but not universal, attributes of urban stream syndrome include (summarized by Paul and Meyer 2001, Konrad and Booth 2005, Meyer et al. 2005, Walsh et al. 2005, O’Driscoll et al. 2010, and Kominkova 2012):
• Increased flashy flows, with (1) more frequent, larger flow events and faster ascending and descending peaks, and (2) reduced groundwater discharge and lower baseflows (Figure 16; although, in some systems, baseflow may be augmented by wastewater treatment plant discharge, lawn irrigation, septic drainage, and other sources). Urban development appears
Amber Darter SSA Page 29 to reduce shallow subsurface flow that supports wet-season baseflow but has a less evident effect on deeper groundwater recharge that supports summertime discharges. Reduced summer baseflows can cause fish mortalities due to reduced flow velocity, cross-sectional area within the channel, and water depth. The Figure 16. Impacts of urbanization on downstream base and peak flows. (Generalized hydrograph comparison from http://ubclfs- increased peak flows wmc.landfood.ubc.ca/webapp/WID/course/land-use-impacts-on-water- after rain events can 3/urban-impacts-13/). wash fish eggs downstream and displace newly-emergent juveniles. Even movements of adults may be limited when water velocity exceeds a species’ swimming speed. High velocities are especially damaging when there is a lack of roughness, such as large woody debris and boulders, which provide eddies where fish can rest (summarized in Finkenbine et al. 2000).
• Altered channel morphology and stability (Figure 17). As each parcel of land is converted to urban use, sediment from construction sites with poor erosion control is transported into streams during rain events, leading to channel aggradation (much like is seen when uplands in a drainage are heavily timbered). After construction ceases, sediment supply is reduced, but bankfull flows are increased owing to increases in EIA. This leads to increased channel erosion as channels incise and widen to Figure 17. Channel changes associated with urbanization (figure from Paul and Meyer 2001). accommodate increased bankfull discharge.
Amber Darter SSA Page 30 During channel evolution, the bed is likely to be unstable at many locations, degrading habitat for spawning, feeding and refugia, especially for the amber darter and other riffle- dwelling species that rely on sediment-free gravel (Wenger and Freeman 2007). The sediment from channel widening and deepening will move through the system, leading to sedimentation and turbidity in downstream habitat. Once a watershed has been urbanized, and the channel has adjusted to the new flow regime, it will no longer be subjected to high sediment loads (Wolman 1967), and bed coarsening is observed (Robinson 1976). However, it can take 15 – 30 years for a streambed to recover from the initially-high sediment loads (Robinson 1976, Klein 1979).
• Increased stream water temperature and urban contaminants due to removal of riparian vegetation and runoff of heated stormwater draining from warmed asphalt, concrete, and other impervious surfaces. Thermal stress may be chronic or acute; acute stress results in immediate mortality, while chronic thermal stress may be one factor contributing to a shift in the fish community structure from intolerant to tolerant (Krause et al. 2004). Elevated nutrients and contaminants from point- and non-point sources are transported in surface runoff or discharged from wastewater treatment plants or other sources (Table 8). The quantity of these pollutants per unit area delivered to receiving waters tends to increase with the degree of development in urban areas.
Of the 537 miles of streams in the Etowah River basin assessed in the Metro Water District, 451 miles, or 84%, did not meet state water quality standards, based on the 2014 303(d) list. The majority of assessed streams (31%) failed standards for fecal coliform bacteria, and another 35% failed standards for fish and macroinvertebrate communities. Biota listings typically indicate high sediment loads in streams, which decreases habitat quality for benthic species (Metropolitan North Georgia Water Planning District 2017).
Table 8. Sources of contaminants in urban stormwater runoff (data from https://www3.epa.gov/npdes/pubs/usw_b.pdf. Contaminant Sources Sediment and Streets, lawns, driveways, roads, construction activities, atmospheric Floatables deposition, drainage channel erosion Pesticides and Residential lawns and gardens, roadsides, utility right-of-ways, Herbicides commercial and industrial landscaped areas, soil wash-off Organic Materials Residential lawns and gardens, commercial landscaping, animal wastes Metals Automobiles, bridges, atmospheric deposition, industrial areas, soil erosion, corroding metal surfaces, combustion processes Oil and Grease/ Roads, driveways, parking lots, vehicle maintenance areas, gas stations, Hydrocarbons illicit dumping to storm drains Bacteria and Viruses Lawns, roads, leaky sanitary sewer lines, sanitary sewer cross- connections, animal waste, septic systems Nitrogen and Lawn fertilizers, atmospheric deposition, automobile exhaust, soil Phosphorus erosion, animal waste, detergents
Amber Darter SSA Page 31 • Reduced fish and macroinvertebrate richness. Wenger et al. (2008) and Wenger (2008) evaluated the relationship of fish occurrence with effective impervious area (EIA) for five Etowah mainstem river species: the amber darter, tricolor shiner, speckled madtom (Noturus leptacanthus), endangered Etowah darter (Etheostoma etowahae), and bronze darter (Percina palmaris) (Figure 19). The bronze darter was selected as a surrogate to supplement limited occurrence data for the amber darter. Response curves indicated that species occurrence probability in a given shoal approached zero at about 5% EIA in the upstream Figure 18. Occurrence probability for (a) bronze and watershed for the bronze darter and 10% (b) amber darter in response to increasing EIA. The dark line represents the response curve based on the EIA for the amber darter (Figure 18). mean parameter EIA estimate. Lighter lines are based Occurrence probability for the Etowah on the 5% and 95% values for the EIA estimate (figure from Wenger 2008). darter, tricolor shiner, and speckled madtom was predicted to approach zero at levels of development equivalent to about 2%– 4% EIA in the surrounding region.
Figure 19. Conceptual model of urban impacts on streams (figure from Wenger et al. 2009). Arrows show selected major pathways, but many important pathways are omitted for readability.
Amber Darter SSA Page 32 Other changes in an urbanizing area include (1) Fewer small streams in the network, as these streams are channelized, hardened or armored with concrete or riprap, culverted for roads and driveways, piped for storm drains, filled to allow land development, impounded for ponds, and other impacts; (2) Loss of mainstem and tributary channels for impoundments for flood control, drinking water, hydropower and other functions; (3) reduced stream flows due to water withdrawals; and (4) removal of riparian vegetation, which reduces stream cover and organic matter inputs, impacts stream temperatures, and leaves banks vulnerable to erosion.
Glyphosate-Based Herbicides: In 1996, Monsanto introduced Roundup Ready® soybean, a genetically-engineered crop resistant to the herbicide glyphosate. Roundup Ready® corn was released in 1998, followed by canola, alfalfa, cotton, and sorghum. All are resistant to glyphosate due to a gene taken from a bacterium, Agrobacterium sp. strain CP4, which has been incorporated into the plant’s genome (Padgette 1995). Glyphosate works by blocking an enzyme in the metabolic route a plant uses to biosynthesize foliates and aromatic acids (aka, the shikimate pathway). The bacterium gene codes for a glyphosate-insensitive form of this enzyme (Funke et al. 2006). Roundup Ready® crops improve a farmer's ability to control weeds, since glyphosate can be sprayed in the fields at any time during the growing season, rather than early in the spring before seedlings emerge. Globally, glyphosate use has risen 15-fold since Roundup Ready® crops were introduced; not only has the herbicide been sprayed on more land acreage, it has been applied more intensively, with more applications per unit area in a given crop year, and at higher one-time rates of application (Benbrook 2016).
Most herbicide formulations are a mixture of an active ingredient (the pesticide) with a variety of “inert” chemicals, such as solvents and surfactants. The original Roundup® formulation included the active ingredient glyphosate, plus the surfactant polyethoxylated tallow amine (POEA), which helps glyphosate better stick to leaves and penetrate plant tissues. Other glyphosate-based herbicides (Table 9) may include POEA or other surfactants (Defarge et al. 2018), and farmers often eschew Roundup® and mix generic glyphosate with dish soap or diesel as the surfactant. Research has documented that glyphosate-based herbicides with POEA are more toxic to fish and other aquatic organisms than glyphosate alone (Folmar et al. 1979, Mitchell et al. 1987, Diamond and Durkin 1997), and POEA is more toxic than Roundup® (Tsui and Chu 2003), particularly in alkaline water vs. acidic water (Diamond and Durkin 1997).
Table 9. Glyphosate-based herbicides and their surfactants (from Defarge et al. 2018). Name Formulant Bayer GC 1–5% POEA Clinic EV 11% POEA Glyfos 9% POEA Glyphogan 15.5% POEA Kapazin C8-10 ethoxylated alcohol (<2 g/L). Triethylene glycol monobutyl ether (<2 g/L) Medallon 10–20% APG (150 g/L) Roundup® Classic 15.5% POEA Roundup® WeatherMax Petroleum distillate/Transorb2
Amber Darter SSA Page 33 In the Conasauga, Lasier et al. (2016) collected post-rainfall surface water and sediment samples from the mainstem and major tributaries 2010-2013 and analyzed for glyphosate and one of its primary breakdown products, aminomethylphosphonic acid, or AMPA. Glyphosate was not detected in any surface water samples (N = 129). AMPA, however, was measured in 77% of the samples, with highest concentrations from the mainstem and tributaries draining the largest farm in the study area. Thirteen samples from the farm sites contained concentrations between 1000 and 5700 μg/L, and roughly 30% of the farm site samples exceeded 400 μg/L. Most of the elevated samples were collected during autumn and winter. The farm sites received discharges from tilled fields, pastures, and a dairy production facility. Glyphosate and/or AMPA (glyphosate and AMPA) were measured in almost all sediments collected from the mainstem and tributaries and ranged from below detection levels to 2428 μg/kg, with mean concentrations for collection sites (n = 9) varying from 200 to 1100 μg/kg.
Current methods for analysis of POEA surfactants require significant time and effort. Lazier et al. (2016) estimated a surfactant concentration between 0.1 and 0.8 mg/L in surface water samples, based on AMPA concentrations (assuming that AMPA levels reflected glyphosate application, the surfactant was equally mobile as AMPA, and the landowner used a standard mix of glyphosate and surfactant). Depending on POEA’s half-life (7-14 days in soil and 21- 42 days in water, Giesy et al. 2000 as cited in Struger et al. 2008, although it may be as low as 13-18 hours, Wang et al. 2005), this chemical’s concentrations in the Conasauga mainstem could quickly fall below acutely toxic levels. However, repeated pulses of POEA (or other surfactants that may impair water quality or aquatic organism health) into surface waters at critical times may impact amber darter survival and recruitment, particularly at shoals adjacent to large farms with greater glyphosate-POEA herbicide application.
Even below lethal levels, glyphosate-based herbicides appear to damage fish DNA. Roundup® produced genotoxic damage in erythrocytes and gill cells of the streaked prochilod (Prochilodus lineatus) (Cavalcante et al. 2008) and caused significant dose-dependent increases in the frequencies of DNA damage in freshwater goldfish (Carassius auratus ) (Çavas and Könen), tilapia (Tilapia rendalli) (Grisolia 2002), and European eels (Anguilla anguilla) (Guilherme et al. 2012). Roundup® exposure caused oxidative stress in the liver and inhibited acetylcholinesterase in muscle and brain of streaked prochilod (Modesto and Martinez 2009); hormone profile and reproductive effects in silver catfish (Soso et al. 2007); and histopathological changes and gill tissue damage in Nile tilapia (Oreochromis niloticus) (Jiraungkoorskul et al. 2003). Langiano and Martinez (2008) noted an increase in plasma glucose and catalase liver activity in streaked prochilod exposed to the herbicide, indicating, respectively, a typical stress response and activation of antioxidant defenses after Roundup® exposure. In addition, Roundup® induced several liver histological alterations that might impair normal organ functioning.
Glyphosate-based herbicides may affect fish behavior. In a laboratory study to evaluate acute toxicity of a glyphosate-based herbicide, juvenile African catfish (Clarias gariepinus) swam erratically, were hyperactive, and had reduced body pigmentation. Faster opercula movement,
Amber Darter SSA Page 34 surfacing, and gulping of air were observed, and, with an increase in duration of the exposure, swimming and body movements were retarded. Later, fish lost balance, became exhausted, and lost consciousness, settling passively at the bottom of the tank with the operculum wide open. They ultimately died (Ani et al. 2017).
Glyphosate's capacity to degrade rapidly is often used to argue against potential long-term toxicological effects associated with application. However, the herbicide is a phosphonic acid (C3H8NO5P), and its degradation in the environment releases inorganic phosphorus. Hebert et al. 2019 summarized the transport of glyphosate in agricultural landscapes (Figure 20): Once sprayed (and ignoring atmospheric loss), glyphosate can either penetrate the soil surface directly or be absorbed by plants via their foliage and translocated via phloem down to the roots, where it is exuded into the soil. In the soil, a fraction of glyphosate can be transported by runoff or can leach into surface waters, either directly following application or after a period of soil storage; another fraction can also be assimilated by nearby non-target plant roots. Most glyphosate, however, will adsorb to soil particles. Soil micro-organisms degrade Figure 20. Transport and degradation of glyphosate in agricultural landscapes glyphosate (figure from Hebert et al. 2019). through two chemical pathways -- one pathway produces AMPA, the second produces the compound sarcosine, which is oxidized to glycine and formaldehyde (Kishore and Jacob 1987, Hebert et al. 2019), and both degradation pathways release inorganic phosphorus. Glyphosate’s application inevitably leads to greater anthropogenic phosphorus input in the agricultural landscapes where it is used and potentially to greater export from soils to water bodies (Hebert et al. 2019).
Lack of Forested Riparian Zones: Riparian zones are lands adjacent to streams, through which overland and subsurface flow paths connect runoff from uplands with waterways (Figure 21).
Amber Darter SSA Page 35
Figure 21. Location of the riparian zone (drawing by Salt Lake County).
Much of the Conasauga mainstem within amber darter habitat, as well as the ditches and tributaries that drain many agricultural fields, lacks a forested riparian buffer or has only fringe vegetation at top of bank. Deforestation of riparian areas can influence the numbers and kinds of organisms in adjacent and downstream reaches. Jones et al. (1999) sampled fishes and stream habitats in Tennessee River tributaries downstream from deforested, but vegetated, riparian patches; all sample reaches were downslope from watersheds with at least 95% forest cover. Darters, sculpins, and benthic minnows decreased in numbers with increasing length of nonforested riparian patch, and sunfishes and water-column minnows increased. Habitat diversity decreased, and riffles became filled with fine sediments as upstream patch length increased. Results suggested that riparian forest removal leads to shifts in the structure of fish assemblages due to (1) decreases in fish species that do not guard hidden eggs or that are dependent on swift, shallow water that flows over relatively sediment-free substrates, or (2) increases in fishes that guard their young in pebble or pit nests or that live in slower, deeper water.
In addition to maintaining habitat for fish and other aquatic organisms, forested riparian buffers play a critical role in protecting stream habitat and water quality by (summarized in Pusey and Arthington 2003, Osborne and Covacic 1993): • Trapping/removing sediment, nutrients, and contaminants from runoff. This function may be greatly reduced or circumvented in the Conasauga, where agricultural ditches conveying runoff bypass the buffer. • Stabilizing streambanks by reinforcing and increasing soil cohesion and providing a protective surface matting. Trees and shrubs use water in the banks and increase drainage, which reduces the risk of bank failure due to saturated soils. Turfgrasses and crops slow runoff, but their root systems are too shallow to provide much streambank stabilization.
Amber Darter SSA Page 36 • Storing and reducing the velocity of floodwaters, lessening the erosive force of a flood. • Shading streams to moderate water temperatures. Lower water temperatures support higher dissolved oxygen levels which are important to maintain fisheries. • Providing leaf litter and large woody debris. Large woody debris creates habitat diversity, provides nutrients for benthic invertebrates, leads to the formation of undercut banks and pools, and shelters fish from high flows and predators (Finkenbine et al. 2000). Leaf litter is an important source of food in smaller stream systems, although in medium-sized rivers, like the Conasauga, aquatic vegetation, algae, and other autochthonous sources likely provide most of the channel’s organic matter (Schlosser and Karr 1981). • Providing habitat for adult insects whose larval forms are aquatic and are a major food source for many freshwater fish.
Decline in the abundance of Podostemum in the Conasauga mainstem: Podostemum is a filamentous dicotyledon that occurs in mid-order montane and Piedmont rivers of eastern North America, where it grows submerged and attached to rocks and stable substrates in swift, aerated water (Figure 22). Widespread declines have been recorded across the species’ range (Wood and Freeman 2017, Davis et al. 2018), including in the Conasauga River. Reasons for the decline are not known but may be related to sedimentation, epiphytic over-growth, hydrologic changes that result in desiccation, and possibly increased herbivory pressure (Wood and Freeman 2017). Figure 22. Podostemum on large cobble.
The presence of Podostemum can alter the physical structure of the channel bed by changing flow regimes (Grubaugh and Wallace 1995), which can affect sedimentation rates, organic deposition rates, and nutrient concentrations in the sediments – flow velocity within Podostemum beds can be decreased by more than 50% compared to flow above the plant beds in a Piedmont stream (Grubaugh and Wallace 1995). The plant stabilizes channel substrate to which it is attached, slowing the rate of downstream bed movement. Podostemum has been shown to increase invertebrate productivity of Piedmont streams (Grubaugh and Wallace 1995). Conversely, reductions in Podostemum biomass have been found to substantially decrease macroinvertebrate biomass, which may trigger trophic cascades that negatively impact fishes and other large bodied consumers (Davis et al. 2018). One hypothesis for the association between benthic fishes, like the amber darter, and Podostemum is preference for sites with increased food availability, but the fishes may also use the plant as a refuge from predators or from swift currents (Argentina 2006).
Amber Darter SSA Page 37 Reservoirs and Dams: The Etowah mainstem is bisected by Lake Allatoona, which was constructed in 1950. The lake impounded the only known amber darter habitat in Shoal Creek, and, given that the current range of the amber darter extends from just upstream of the lake, it is likely that, historically, the fish occurred in mainstem reaches currently flooded by the lake. We have no records of amber darters downstream of Allatoona Dam, currently or historically, and current dam operation likely limits suitable habitat -- reservoirs can substantially alter hydrology downstream, especially when dams, like Allatoona, are operated for hydroelectric power generation (Figure 23). Hydropeaking dams release high flows only when power generation is needed. These large and rapid changes in discharge result in a pulsing-flow cycle very different from a natural flow regime. Water released from Lake Allatoona is pulled from the lower lake levels, and these releases are both colder than natural water temperatures and oxygen depleted. Flashy flows, cold water, low dissolved oxygen, and likely scouring of sediments due to repeated high flows (Cushman 1985) may be factors in the absence of amber darters in the Etowah mainstem below Allatoona (if they occurred there historically). Zhong and Power (1996) found dam construction in China blocked fish migrations, delayed spawning 20-60 Figure 23. Etowah River hydrograph from USGS gage 02394670 downstream of days due to lower Allatoona Dam. The dam generates power on most weekdays. The Conasauga is water temperatures, unimpounded, and its hydrograph shows natural flows.
Amber Darter SSA Page 38 caused some spawning grounds below the dams to be abandoned, and led to extinction of one fish species.
Non-hydropeaking reservoirs, farm ponds, amenity lakes, and other impoundments also may alter hydrologic regimes by storing water during low flow periods, effectively dampening moderate to high flows and in some cases augmenting low flows in the mainstem. Recent studies in the Georgia Piedmont show that fish assemblage integrity levels decline as water withdrawal levels increase (Freeman and Marcinek 2006). In addition to the many small farm ponds and other impoundments that dot tributaries in the upper Conasauga and Etowah River basins, three new drinking water reservoirs serving thousands of local citizens have been/are being constructed on tributaries to the Upper Etowah River, including: • the 334-acre Hollis Q. Lathem Reservoir on Yellow Creek in Cherokee County, which began construction in 1997 and reached full pool in 2002. • the 411-acre Hickory Log Creek Reservoir in Cherokee County, which began construction in 2004, was completed in 2007, and filled by 2010. • the 137-acre Russell Creek Reservoir in Dawson County, which the Corps of Engineers, Savannah District, permitted under Section 404 of the Clean Water Act in 2017. Timber harvest will begin winter 2019, and the reservoir will be completed and filled by 2024.
None of these Conasauga or Etowah impoundments directly fragments amber darter habitat, like Lake Allatoona and Dam do, but land clearing and reservoir operation can affect mainstem water quality and alter the natural hydrologic regime in amber darter habitat.
Climate Change: Earth’s average surface temperature has risen 1.62F since the late 19th century, a change driven largely by increased carbon dioxide and other human-made emissions into the atmosphere. Most of the warming occurred in the past 35 years, with the five warmest years on record since 2010. The oceans have absorbed much of this increased heat, with the top 700 meters (about 2,300 feet) of ocean showing warming of more than 0.4 degrees Fahrenheit since 1969. (NOAA https://climate.nasa.gov/causes/).
Climate change may increase extinction risk for many terrestrial and freshwater species during and beyond the 21st Century. The Fourth National Climate Assessment, released by the U.S. Global Change Research Program in November 2018, states “Observations collected around the world provide significant, clear, and compelling evidence that global average temperature is much higher, and is rising more rapidly, than anything modern civilization has experienced, with widespread and growing impacts. The warming trend observed over the past century can only be explained by the effects that human activities, especially emissions of greenhouse gases, have had on the climate.” The Assessment stated annual average temperature over the contiguous United States increased 1.2°F (0.7°C) for the period 1986–2016 relative to 1901–1960 and projected, with high to very high confidence, that (Jay et al. 2018):
Amber Darter SSA Page 39 • Annual average temperature over the contiguous United States would rise about 2.5°F (1.4°C) for the period 2021–2050 relative to the average from 1976–2005, with greater changes at higher latitudes as compared to lower latitudes. • Additional increases in temperatures across the contiguous United States of at least 2.3°F relative to 1986–2015 are expected by the middle of this century. • By late this century, increases of 5.4-11°F would occur if immediate and substantial mitigation to reduce greenhouse gas emissions was not implemented by mid-century, with greater reductions thereafter (Scenario RCP8.5; status quo). Increases of 2.3°–6.7°F were expected even under a scenario (RCP4.5) where late century global annual carbon emissions were significantly reduced (85%) relative to today (Figure 24). • High temperature extremes, heavy precipitation events, high tide flooding events along the U.S. coastline, ocean acidification and warming, and forest fires in the western United States and Alaska will continue to increase. • Land and sea ice cover, snowpack, and surface soil moisture will continue to decline.
The effects of climate change on aquatic species in the Conasauga and Etowah Rivers have not been studied. In the Southeast through the 21st century, variability in weather is predicted to Figure 24. Projected changes in US annual average temperatures. The increase, resulting in more RCP8.5 scenario assumes current trends in annual greenhouse frequent and extreme dry emissions continue. The RCP4.5 scenario envisions 85% lower greenhouse gas emissions than RCP8.5 by the end of the 21st century and wet years over the next century (Mulholland et al. 1997, Ingram et al. 2013). 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, heat waves will become longer, temperatures exceeding 95F will increase, sea levels will rise an average of 3 feet, the number of category 3 to 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 agricultural irrigation, and increasing toxicity of pollutants (Ficke 2007, Rahel and Olden 2007). Reduced spring/summer rainfall, coupled with increased evapotransporation and water demand (because of population growth), could lead to local extirpations if streams dry out more frequently (Ingram et al. 2013). Fishes not constrained by movement barriers could move upstream to cooler waters; however,
Amber Darter SSA Page 40 even historically, the amber darter was not known to occur in the Conasauga much above the TN Hwy 74 crossing, in the Etowah above Dawson Forest Wildlife Management Area, or in tributaries except close to the confluence with the mainstem river. These upstream areas may be too small, have unsuitable geomorphology, or have unsuitable water chemistry to support the species.
Conservation Actions Habitat for the amber darters is protected, to varying degrees, under the State of Georgia’s Endangered Wildlife Act of 1973 (O.C.G.A. 27-3-130 et seq.), Tennessee Nongame and Endangered or Threatened Wildlife Species Conservation Act of 1974 (Tenn. Code Ann. § 70-8- 101), Georgia Erosion and Sedimentation Act (O.C.G.A. 12-7-1 et seq.), Tennessee Water Quality Control Act of 1977 (Tenn. Code Ann. § 69-3-102), other State laws and regulations regarding natural resources, the Federal Endangered Species Act (Act) of 1973, as amended (16 U.S.C. §1531 et seq.) and Clean Water Act (33 U.S.C. §1251 et seg.). The Georgia Endangered Wildlife Act limits protection of listed species to individuals found on State public lands (excluding Georgia Department of Transportation lands). Individuals on private lands are not protected under State law. The Tennessee Nongame and Endangered or Threatened Wildlife Species Conservation Act is more stringent – it makes it unlawful for any person to take, attempt to take, possess, transport, export, process, sell or offer for sale or ship nongame wildlife.
Georgia’s Erosion and Sedimentation Control Act was passed in 1975 to protect Georgia’s waters from soil erosion and sediment deposition. The Act requires an erosion, sedimentation, and pollution control plan for land-disturbing activities on sites >1 acre. Major BMP violations were observed at 60% of over 100 construction sites evaluated in 2005 (Upper Chattahoochee Riverkeeper 2006) and included failure to install and/or maintain BMPs, illegal stream buffer encroachments, poor or nonexistent BMP design plans, and sediment entering state waters. The Act also mandates minimal stream buffer protection -- a 25-foot buffer between a permitted land- disturbing activity and a non-trout streams -- and a buffer variance may be obtained. The Tennessee Water Quality Control Act requires a 60-foot natural riparian buffer between a land-disturbing activity and a receiving stream designated as impaired or an Exceptional Tennessee waters. A 30- foot natural riparian buffer zone is required adjacent to all other streams.
Agriculture and forestry are fully or partially exempted from regulation under Georgia’s Erosion and Sedimentation Control Act and the Tennessee Water Quality Control Act. The States address threats associated with agriculture and silviculture primarily through voluntary State BMPs. A 2017 Statewide Forestry BMP survey in Georgia (Georgia Forestry Commission 2017) found correct BMP implementation at 92% of 232 sites evaluated, and 92.8% and 88.2% implementation of streamside management zone (SMZ) and stream crossing BMPs. The most common SMZ deficiencies were insufficient widths, logging debris left in stream channels, poor water diversions/ stabilization, and streambank harvesting. Deficiencies in stream crossing BMPs included stream crossing design, culvert sizing and installation, and the use of improper debris crossings and fill. Similarly, the Tennessee Division of Forestry from spring 2010 through winter 2011 evaluated
Amber Darter SSA Page 41 compliance with 53 individual forestry BMPs. Implementation of BMPs to protect stream health was slightly lower than observed in Georgia, with an average of 78 and 88% of BMPs associated with SMZ and stream crossings installed correctly (Sherrill et al. 2013).
The degree of compliance with BMPs for agricultural activities has not been systematically measured (or encouraged) in either state.
Conservation partners have conducted research to identify stressors on rare species in the Conasauga and Etowah basins and implemented on-the-ground management actions, including: • Research by USGS, the University of Georgia, the Tennessee Aquarium, and others to identify stressors in the Conasauga and Etowah basins, including evaluation of water quality and algal blooms in the mainstem, response of fishes to stormwater runoff and other stressors associated with urbanizing areas, identification of tributaries delivering the greatest nutrient and contaminant loads, and evaluation of environmental estrogens and intersex fish. • Monitoring fish population trends in the Conasauga and Etowah basins. The University of Georgia, Georgia Department of Natural Resources, Conservation Fisheries, Tennessee Aquarium, Dalton Utilities, Dinkins Biological Consulting, and Cobb County-Marietta Water Authority (via CCR Environmental) have surveyed fish communities at fixed locations in the Upper Etowah and Conasauga, with databases reaching back over two decades. • Implementation of management actions to restore streams and floodplains in priority habitat for the amber darter and other rare aquatics in the Conasauga and Etowah basins. National Forest Service land protects the headwaters of both rivers (Chattahoochee and Cherokee National Forests). NRCS, The Nature Conservancy, Limestone Valley RC&D, GDNR, Conasauga and Upper Etowah River Alliances, Forest Service, USFWS, and others have long worked in the Upper Coosa basin to improve water quality and wildlife habitat. • Land protection/conservation. In addition to the Cherokee and Chattahoochee National Forests, the Georgia Department of Natural Resources owns or manages over 7,000 acres adjacent to the Etowah mainstem in the amber darter range (Dawson Forest and McGraw Ford Wildlife Management Areas). Joint efforts by conservation partners have permanently protected an additional 4,500 and 8,715 acres, respectively, within or upstream of the amber darter range (Table 10). • Development of a Working Lands for Wildlife-Conasauga program to reduce nutrient input into the river and its tributaries, in addition to multiple conservation actions implemented under Farm Bill programs. • Development of policies and ordinances, which can be adopted by participating local governments, that modify current development practices regarding infiltration of stormwater runoff, better site design, limits on mass grading, retention of riparian buffers, and sediment/erosion control. • Regular meetings with partners to discuss recent biological monitoring trends, scientific research, threats, and possible solutions to alleviate those threats.
Amber Darter SSA Page 42 Table 10. Conservation lands on or immediately adjacent to the Conasauga and Etowah River mainstems. List excludes acreage in the Chattahoochee and Cherokee National Forests. Conasauga Conservation Properties Acres Etowah Conservation Properties Acres Georgia Alabama Land Trust mitigation lands 2267 Dawson Forest WMA 4830 Taylor Branch Howell Tract 616 McGraw Ford WMA 2255 Alaculsy Mitigation Bank 508 Deerleap Conservation Bank 940 Upper Coosa Mitigation Bank (proposed) 415 Eagle Point Landfill mitigation 249 Conasauga River WMA 314 Etowah River Preserve Bank 172 Dalton Utilities Spring Creek Preserve 221 Etowah River Road Mitigation Bank 135 Prater Island Mitigation Site 105 Applewood Mitigation Bank 81 Conasauga Bend Mitigation Bank (proposed) 89 Yahoola Reservoir David Tract 30 Etowah River Mitigation Bank 23 Total 4,535 8,715
Amber Darter SSA Page 43 AMBER DARTER FUTURE CONDITION: VIABILITY TO 2060
This SSA has considered what the amber darter needs to be viable, the current condition of those needs, and the stressors that are driving the historical, current, and future conditions of the species. In this section, we predict the species’ future viability, which we defined as the ability of the species to maintain self-sustaining populations throughout known historic ranges in both the Conasauga and Etowah Rivers through 2060. Self-sustaining populations are those that are sufficiently abundant and have sufficient genetic diversity to display the array of life-history strategies that will provide for persistence and adaptability over time (Committee of Scientists 1999) and in the face of environmental stochasticity, catastrophes, and changes in its biological and physical environment. We did not include the Coosawattee River in our analysis, since we have no data suggesting a permanent amber darter population currently or historically in this river. We chose the 2060 timeframe to match a SLEUTH model that projected 2060 urban growth patterns for the US Southeast. A SLEUTH model simulates four types of urban growth patterns: spontaneous growth, new spreading urban centers, edge growth around existing urban areas, and road-influenced growth.
Scenarios: We evaluated three future scenarios: • Current stressors and conservation actions continue at current levels. • Current stressors in both basins are exacerbated by high spring flows two years in a row. • A best-case scenario, where new populations are located (redundancy), connectivity is restored (replication), and/or conservation agencies work strategically, at a large enough scope, to reduce stressors and enhance resiliency.
Assumptions: Under all three scenarios, we assumed: • The impact of climate change on amber darter habitat increased over time. • Urbanization continued in the Etowah River basin (Figure 25). The SLEUTH model predicted the largest change in percent of land urbanized in the Southeast US by 2060 would be in the Piedmont, including the Atlanta metro area, and that a megalopolis from Raleigh, NC to Atlanta, including the Etowah basin, would expand and become less fragmented (Terando et al. 2014). Figure 25. Projected urban land cover in the Southeast US in 2060 • Land in the Conasauga River’s (figure from Terando et al. 2014). Red arrows point to the general location of the Conasauga and Etowah basins. floodplains continues to be
Amber Darter SSA Page 44 farmed through 2060, although crops and agricultural practices might change and alter the type and/or magnitude of threat. Future urban growth in the Conasauga was assumed to have greater impact on uplands drained by tributary systems, with the main impact on the mainstem being degraded water quality associated with increased sediment and urban contaminant loading.
Current Stressor/Conservation Action Scenario: There are only two populations of amber darters, and count data indicate both are declining. MARSS analysis, conducted by the University of Georgia and USGS, estimated that amber darters declined approximately 12% annually in the Conasauga and 9% annually in the Etowah River over the past two decades (Stowe et al. 2019). Occupancy of shoals declined in the Conasauga (Freeman et al. 2017) during this 20-year period, and amber darter abundance in both systems was greatly reduced in the lower reaches of the historic range (see pages 12-15 of this SSA for greater detail). As numbers declined, each population has become more vulnerable to environmental, demographic, and genetic stochastic processes. Under this scenario, analyses suggest that, at current rates of decline, amber darters would be effectively undetectable (defined as a catch-per-unit-effort of 1 fish in 400 seine-sets at a given shoal by experienced field biologists) between 2021 and 2032 in the Conasauga and 2030 and 2047 in the Etowah (Edward Sage Stowe, UGA, and Mary Freeman, USGS, pers. comm., November 2018).
Current Stressor/Conservation Action with High Spring Flow Scenario: Spring floods may be a factor limiting amber darter recruitment. Hagler and Freeman (2014) found evidence of a negative effect of increasing the minimum 10-day moving average in spring, suggesting the amber darter benefits from windows of low spring flow for spawning and recruitment success. High flows may damage eggs, wash larvae from nursery areas, prevent juveniles from migrating upstream to suitable shoal habitat, and increase turbidity and sedimentation that degrades habitat. The fish’s maximum life span is four years, and high spring flows in successive years that limit or eliminate juvenile recruitment would significantly depress population numbers. Under this scenario, amber darters are likely to become effectively undetectable even more quickly than in the previous scenario.
Best-Case Scenario – Improving Resiliency, Redundancy, and Representation: The future viability of the amber darter, given current stressors and documented population declines in both the Conasauga and Etowah, appears dire. However, amber darters have recovered from low, undetectable numbers before. From 1948-1990, only a single amber darter was collected in the Etowah, despite intensive surveys. The population recovered, although genetic diversity was reduced (e.g., a bottleneck; see page 15 of this SSA).
Under a best-case scenario, redundancy, representation, and resiliency could be improved if: • The number of amber darter populations increases. Recovery would be significantly enhanced if a third viable population was discovered. Extensive sampling in the Upper Coosa, however, over several decades has located only a single amber darter outside the known historic range -- in the Coosawattee in 2010. (Note: The Guidelines for Propagation and Translocation for Freshwater Fish Conservation (George et al. 2011) state that introductions should never be made outside of a species historic range, regardless of its imperilment).
Amber Darter SSA Page 45 • Population connectivity is increased. Natural connectivity between the Etowah and Conasauga populations could be enhanced if Allatoona Dam was removed. This, too, is unlikely. The lake supplies much of the drinking water for three Georgia counties and provides economic benefits and recreational opportunities to surrounding communities and the State of Georgia. We could propagate and translocate individuals between the two known populations to increase genetic diversity, but such management actions would be of limited value until anthropogenic stressors driving these species’ decline are alleviated. • The impact of stressors is reduced. In a best case scenario, targeted management actions are applied immediately and at a sufficiently large scale, with a focus on priority tracts, to reduce the impact of stressors. As habitat quality improves, survival and recruitment increase, and populations grow to a sustainable size and spread to occupy most or all of their historic habitat. Targeted management actions identified in the 2019 Amber Darter Recovery Implementation Schedule include: 1. Implementing management actions and encouraging best management practices to improve water quality in both the Conasauga and Etowah River mainstems. 2. Protecting, and restoring, if needed, key parcels via land acquisition, conservation agreements, and conservation easements in both basins. 3. Promoting voluntary stewardship to reduce pollution and improve habitat. 4. Working with local/county/state governments to develop and implement ordinances regulating stormwater management and earth-moving activities, establishing stormwater utility fees, and other actions to address urban stressors on aquatic systems. 5. Conducting research to determine the species’ demographics and threat sensitivity to aid recovery efforts for the amber darter. 6. Increasing public awareness through outreach materials, festivals, planned snorkel and canoe/kayak trips, and other methods. 7. Modifying State and local government policies and regulations to improve protection of the fish and its habitat and enhance enforcement of such policies and regulations.
This scenario does not assume utopic conditions are achievable. Some levels of ongoing detrimental anthropogenic influences are anticipated to continue on the landscape that cannot be fully mitigated, and the species likely would still occupy fewer shoals, with less connectivity, than was available relative to pre-European settlement conditions. Those influences would be addressed to the point where population resiliency affords high levels of resistance to stochastic events.
Summary: Both current and worst-case scenario forecasts predicted significant future declines in amber darter populations, to a status where they effectively are undetectable during fish collections, well before 2060. However, the rate of this decline, or whether it occurs at all, depends largely on the likelihood of future management actions that target priority stressors on priority tracts of land, at a watershed scale, in a timely manner (i.e., before either population is extirpated), and with provisions to protect habitat from foreseeable threats in the future.
Amber Darter SSA Page 46 Table 11. Summary of amber darter needs, current conditions, and viability to 2060. Future Viability Species Needs Current Conditions Current Stressor Best Case Scenario and High Spring Flow Scenarios Resiliency: Large populations able to withstand stochastic events High quality shoal Narrow endemic species Viability models Resiliency dependent habitat with areas of with only two small suggest that, at on (1) funding levels; moderate water depth populations and limited current rates of (2) scale of flowing over geographical ranges. decline, amber implemented substrate dominated Count data from surveys darters would be management actions by moveable gravel over almost two decades effectively relative to watershed and small cobble. indicate both are declining undetectable size and degree of Adequate water 9-12% annually. between 2021 and threat; (3) ongoing quality and food Occupancy of shoals has 2032 in the stochastic stressors; (4) availability. Sexually- declined in the Conasauga, Conasauga, and how quickly mature males and and fish in both systems 2030 and 2047 in management actions females in a shoal. have been extirpated or the Etowah. are implemented; and Low spring flows for greatly reduced in (5) the effects of spawning. abundance in the lower climate change on Connectivity among reaches of the historic species’ demographics. shoals. Sufficient range. numbers to withstand stochastic events. Resiliency low to very low. Redundancy: Number and distribution of populations to withstand catastrophic events Multiple resilient Only two populations are With only two Redundancy dependent populations widely known historically, and populations, both in on (1) increased distributed across the neither appears resilient sharp decline, resiliency of species’ historic to stochastic or redundancy is likely Conasauga and Etowah range. catastrophic events to remain low, populations (see above) and/or to current unless additional, and (2) potential for anthropogenic stressors. viable populations locating and conserving are located outside existing populations Redundancy low. of the species outside of the known historical Conasauga and Etowah range. systems.
Representation: Genetic and ecological diversity to maintain adaptive potential Decreased inbreeding Two declining Genetic diversity Genetic diversity likely and reduced negative populations genetically- likely to decline as to decline due to genetic impact of genetic drift isolated by Lake population numbers isolation unless and deleterious Allatoona. are reduced and Allatoona Dam is mutations on viability. genetic isolation removed and/or Low to Moderate remains. individuals are Representation translocated between the two populations.
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