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Conclusions and Future Directions: Ecology and Conservation of the Threatened Blackside Dace, Chrosomus cumberlandensis
Hayden T. Mattingly and Michael A. Floyd

Southeastern Naturalist, Volume 12, Special Issue 4 (2013):181–188

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181 H.T. Mattingly and M.A. Floyd 2013 Southeastern Naturalist Vol. 12, Special Issue 4 Conclusions and Future Directions: Ecology and Conservation of the Threatened Blackside Dace, Chrosomus cumberlandensis Hayden T. Mattingly1,* and Michael A. Floyd2 Summary and Common Themes The 12 articles in this volume collectively contain a wealth of new information regarding the ecology and conservation of Chrosomus cumberlandensis (Starnes and Starnes) (Blackside Dace). Notable findings of each article are summarized in Table 1. Although each article addresses its own particular set of questions and objectives, a number of common themes emerge from the collection. In the following paragraphs we highlight several themes that merit attention. Threats and impacts are still occurring. Despite the advantage of legal protections provided by federal and state regulatory mechanisms, Blackside Dace populations continue to be exposed to threats across much of their distributional range. Human-induced impacts associated with extraction of natural resources, construction of road crossings, channelization of streams, alteration of riparian zones, as well as impacts from Castor canadensis Kuhl (Beaver) are all touched upon in this volume. McAbee et al. (2013), Bivens et al. (2013), and Black et al. (2013b) noted empirical evidence and expert opinion regarding impacts of coal mining on stream water quality. Rakes et al. (2013) propagated dace in captivity for use in toxicity studies related to degraded water quality. Mattingly and Black (2013) observed degradation of four stream habitat variables at sites adjacent to active logging operations. Papoulias and Velasco (2013) detailed the waterquality changes and fish-tissue damage caused by hydraulic fracturing-fluid releases associated with development of natural gas wells. Eisenhour and Floyd (2013) and Floyd et al. (2013) discussed effects of perched culverts, stream channelization, and poorly maintained riparian zones. Finally, Compton et al. (2013) chronicled the collapse of a dace population in a watershed where Beavers altered the stream’s hydrology and ecology. Conductivity appears to be an important water-quality parameter. Black et al. (2013b) observed that Blackside Dace are more likely to be present and persist in stream reaches where conductivity values are <240 μS/cm. Stream size (link magnitude) and water temperature played supportive roles alongside conductivity in the strongest reach-scale habitat models. McAbee et al. (2013) also found that coal-mining impacts such as elevated conductivity were the most influential variables affecting predictions of dace population persistence in their analyses. The mechanism underlying the tendency for dace to be absent in reaches with elevated 1Department of Biology, Box 5063, Tennessee Technological University, Cookeville, TN 38505. 2US Fish and Wildlife Service, 330 West Broadway, Suite 265, Frankfort, KY 40601. *Corresponding author - Ecology and Conservation of the Threatened Blackside Dace, Chrosomus cumberlandensis 2013 Southeastern Naturalist 12(Special Issue 4):181–188 H.T. Mattingly and M.A. Floyd 2013 Southeastern Naturalist 182 Vol. 12, Special Issue 4 conductivity is not fully understood at this time. Elevated conductivity could have direct negative effects, it could represent a lingering indicator of previous waterquality degradation, or it could be acting in both capacities. Furthermore, a variety of land-use disturbances in a watershed can produce high conductivity levels and the chemical composition of elevated-conductivity waters (e.g., concentrations of sulfate and chloride ions) can vary depending on the type of disturbance. Table 1. Selected findings of 12 articles contained in the special issue on Chrosomus cumberlandensis (Blackside Dace) ecology and conservation. Dace = Blackside Dace. Authors Abbreviated title Black et al. (2013a) Population densities • Only 41 of 119 surveyed reaches had single-pass electrofishing catch rates >10 dace per 200 m. • In the 78 occupied reaches, mean electrofishing catch was 27 dace per 200 m and maximum catch was 151 dace per 200 m. • In the occupied reaches, mean population estimate was 90 dace per 200 m and mean density estimate was 14 dace per 100 m2. Black et al. (2013b) Habitat models • Presence of dace was associated with variables such as gradient (stream spatial scale) and conductivity, dissolved oxygen, link magnitude, percent riffle, temperature, and turbidity (reach spatial scale). • Habitat models were validated by collecting additional data at both spatial scales, and all topperforming models included water conductivity as a predictor variable. • Optimal reach-scale summertime conditions favoring dace presence and persistence include conductivity <240 μS/cm, temperature <19 °C, and link magnitude between 3 and 6. Mattingly and Black (2013) Nest association • All 25 dace spawning events observed in a field setting occurred over Semotilus atromaculatus (Creek Chub) nests during 12 May–12 June 2006 at water temperatures between 11.9–18.2 °C. • Dace spawning microhabitats were in areas with greater channel widths, slower water velocities, lower silt levels, lower substrate embeddedness, and larger subdominant substrate particles compared to non-spawning microhabitats. • Study reaches with nearby logging activities had greater mean silt levels, substrate embeddedness, water temperature, and conductivity values compared to reaches with no active logging. Detar and Mattingly (2013) Movement patterns • Most dace, 81% in Big Lick Branch and 58% in Rock Creek, were recaptured in the same 200-m reach in which they were initially marked, suggesting a large sedentary group and a smaller mobile group in each population. • Several dace moved considerable distances (up to 4 km) from their initial marking site in one year, including the first documented intertributary movements for th is species. Eisenhour and Floyd (2013) Culvert barrier • The fish assemblages upstream and downstream from a perched culvert in Lick Fork were markedly different, with lower species richness and biotic integrity observed upstream. • Upstream dace abundance declined during the study period due to periodic drought conditions, stream channelization, and the presumed inability of dace to pass through the culvert barrier to recolonize upstream habitats. Papoulias and Velasco (2013) Hydraulic fracturing fluids • Release of hydraulic fracturing fluids into Acorn Fork resulted in water conductivity of 35,000 μS/cm, pH of 5.6, and mortality of dace. • Fish exposed to degraded Acorn Fork waters showed general signs of stress and exhibited more gill lesions than unexposed reference fish. 183 H.T. Mattingly and M.A. Floyd 2013 Southeastern Naturalist Vol. 12, Special Issue 4 Additional research and monitoring along these lines should yield valuable insights regarding conductivity and its influence on dace populations. Many populations are small and vulnerable. As reported by Black et al. (2013a), many Blackside Dace populations occur at undesirably low densities and, therefore, are vulnerable to local extinction. These populations could be recolonized by individuals from nearby populations but only if adjacent populations are present, unobstructed movement corridors exist, and local conditions Table 1, continued. Authors Abbreviated title Compton et al. (2013) Beavers in Davis Branch • The fish community in Davis Branch, surveyed during 1990–2010, changed spatially and temporally in reference to Beaver colonization (1994) and subsequent alteration of the stream ecosystem. • Relative abundance of Lepomis auritus (Redbreast Sunfish), L. gulosus (Cuvier in Cuvier and Valenciennes) (Warmouth), and Chrosomus erythrogaster (Southern Redbelly Dace) increased following Beaver colonization and pond establishment. • After Beaver establishment, the once-healthy dace population in Davis Branch eventually collapsed, with only one individual encountered during 2008–2010 surveys. Floyd et al. (2013) Mill Branch restoration • A 739-m habitat restoration (reconfiguration) was completed on Mill Branch in Knox County, KY. Fish community richness increased within both restored reaches of Mill Branch; fish diversity and evenness increased within the upstream restored reach. • No significant change was detected in the dace population; however, completion of the project means dace movement within Mill Branch is no longer restricted by a perched culvert, the downstream reach has perennial flow, and a 739-m reach of Mill Branch is protected from future habitat disturbance. McAbee et al. (2013) Bayesian-belief network model • A Bayesian-belief network (BBN) model predicting the response of dace populations to human, environmental, ecological, and biological parameters was developed using data from both empirical studies and expert judgment. • BBN sensitivity and scenario-building analyses indicated that mining practices and water conductivity affected predictions of dace population response much more than other abiotic model parameters. Rakes et al. (2013) Captive propagation • Dace spawned in captivity during April and May 2011–2013 at water temperatures between 16–21 °C, with offspring successfully reared to the juvenile stage in all three years. • Dace spawned when cued by addition of heterospecific milt in 2011 and 2012, but spawned independently in 2013 without the presence of other fishes or th eir milt. Bivens et al. (2013) Big South Fork populations • Between 1999 and 2006, dace populations were discovered in 8 tributary streams in the Big South Fork Cumberland River drainage in KY and TN, representing a downstream extension of the species’ known range in the Cumberland River system. Skelton (2013) Virginia populations • Dace populations were recently discovered in tributary streams in the North Fork Powell and upper Clinch river systems, representing an extension of the species’ known range to a new drainage (Tennessee River) and new state (Virginia). • Molecular, distributional, and anecdotal evidence indicate that dace were introduced to Virginia by humans from neighboring Cumberland River tributary streams i n Kentucky. H.T. Mattingly and M.A. Floyd 2013 Southeastern Naturalist 184 Vol. 12, Special Issue 4 are improved to support a healthier population. Some streams may naturally support smaller populations than others, but we suspect that the threats and impacts discussed above are partially responsible for the low densities seen in many locations. Vulnerable populations will likely require protection, more management actions, and frequent monitoring to increase the likelihood that they will persist. Movement and free passage are necessary. Detar and Mattingly (2013) observed Blackside Dace movement patterns over an annual cycle and found both sedentary and mobile individuals in the study populations. Some individuals moved considerable distances away from their tagging sites, including movements into and out of nearby tributary streams. Detar and Mattingly (2013) cited multiple benefits of such movements to enhance the short- and long-term viability of dace populations. The negative consequences of stream obstructions were vividly detailed in case studies by Eisenhour and Floyd (2013), Floyd et al. (2013), and Compton et al. (2013) in which perched culverts and beaver dams led to fish-community changes and Blackside Dace declines. The implications of these studies suggest more attention be paid to placement and proper design of road crossings to facilitate unfettered fish passage. In addition, stream habitat and water quality should be protected to maintain suitable movement corridors within and among dace populations. The integrity of the stream community should be maintained. Several articles point to the importance of ecological interactions between Blackside Dace and other species. Mattingly and Black (2013) examined the vital role of other minnow species, particularly Semotilus atromaculatus (Mitchill) (Creek Chub), that create spawning microhabitat for Blackside Dace, while Rakes et al. (2013) evaluated the role of milt from other species in a hatchery setting. Blackside Dace spawning in the wild appears primarily dependent on Creek Chub nest construction and maintenance. Compton et al. (2013) documented how Blackside Dace can be affected by system-wide changes induced by Beaver activities. Compton et al. (2013) also stated that Chrosomus erythrogaster (Rafinesque) (Southern Redbelly Dace) may act as a competitor with Blackside Dace, especially under disturbed stream conditions, although these authors did not speculate for which resources the two species might compete and at which times these resources might be in limited supply. Even though non-native species represent only a small percentage of fish species richness in upper Cumberland River tributary streams, their potential impacts are not thoroughly understood. Lepomis auritus (L.) (Redbreast Sunfish) is an introduced species that Compton et al. (2013) and Floyd et al. (2013) speculated could be preying on Blackside Dace in certain situations. Additional ecological research is needed to evaluate the putative roles of Southern Redbelly Dace as competitor, and Redbreast Sunfish as predator. We also note that two other imperiled fishes, Etheostoma sagitta (Jordan and Swain) (Cumberland Arrow Darter) and E. susanae (Jordan and Swain) (Cumberland Darter), are native to the upper Cumberland River drainage and currently are found in >30 of the same tributary streams as Blackside Dace. Taken together, these observations reinforce the notion that maintaining high-quality stream 185 H.T. Mattingly and M.A. Floyd 2013 Southeastern Naturalist Vol. 12, Special Issue 4 habitats and native fish communities will enhance Blackside Dace conservation efforts by ensuring the presence of nest hosts, reducing potential pressures of competition and predation, and preserving sympatric imperiled fi sh species. Distribution and abundance are only partially known. The articles by Bivens et al. (2013) and Skelton (2013) serve as valuable reminders that more work is needed to better understand the full extent of the dace’s distributional range. The remote location and small size of many streams offer the possibility that additional populations will be discovered. Black et al. (2013a) discussed how the abundance of Blackside Dace in selected populations has changed since previous surveys, usually in a negative direction. Unauthorized introductions of Blackside Dace by humans into new watersheds, as noted by Bivens et al. (2013) and Skelton (2013), warrant more attention by researchers and managers. These findings suggest that ongoing surveys and population monitoring will be needed to maintain knowledge of the current status of Blackside Dace populations. Future Directions for Research and Recovery Our second goal in this essay is to discuss future directions for Blackside Dace research and recovery activities. Several years before publication of this volume, 15 Blackside Dace experts were asked to rate the amount of uncertainty regarding knowledge of Blackside Dace biology and ecology in a number of categories (Supplemental Appendix 1 in McAbee et al. 2013). Most species experts responded that identification, distribution, abundance, habitat requirements, reproduction, and adult life history were either well known or moderately known (Table 2). However, Blackside Dace ecological interactions, behavioral patterns, and early life history were rated as poorly known. We combined the information in Table 2 with the common themes identified above to highlight a number of Table 2. Response of 15 Blackside Dace species experts (defined in McAbee et al. 2013) to a survey question asking them to rate the current state of knowledge regarding Blackside Dace ecology. Table values are the percentage of survey participants responding in each of the four categories, rounded to nearest whole numbers. For example, 13% of the species experts stated that Blackside Dace abundance was “well known”, 77% selected “moderately known”, 10% selected “poorly known”, and none selected “completely unknown”. Current state of knowledge regarding Blackside Dace Completely Ecological category Well known Moderately known Poorly known unknown Identification 100 0 0 0 Distribution 40 60 0 0 Abundance 13 77 10 0 Habitat requirements 7 90 3 0 Ecological interactions 0 39 61 0 Behavioral patterns 0 43 57 0 Reproduction 7 73 20 0 Early life history 0 20 80 0 Adult life history 0 86 14 0 H.T. Mattingly and M.A. Floyd 2013 Southeastern Naturalist 186 Vol. 12, Special Issue 4 research projects for future consideration. The projects are listed below in no particular order of priority. • Investigate the response of Blackside Dace to elevated water conductivity. For example, information is needed regarding the chemical components of elevated-conductivity waters and whether or not specific constituents exhibit toxicity (acute, chronic, lethal, sublethal) to different life stages of dace (i.e., gametes, embryos, larvae, juveniles, adults). • Evaluate the swimming performance of Blackside Dace to inform the design and placement of bridges, culverts, and other structures allowing fish passage. • Determine Blackside Dace genetic diversity and level of genetic exchange among populations. Genetically unique or isolated populations may warrant special management attention. • Develop a cost-effective and statistically sound monitoring strategy for Blackside Dace populations and stream water quality in the upper Cumberland River drainage. • Predict the response of Blackside Dace populations to potential invasion of their watersheds by Adelges tsugae Annand (Hemlock Woolly Adelgid) and the corresponding loss of Tsuga canadensis (L.) Carriere (Eastern Hemlock) along riparian zones. • Predict the response of Blackside Dace to climate change, specifically addressing how stream habitat conditions such as water temperature and discharge are likely to change and how the species might adapt to changing conditions. • Study Blackside Dace behavioral and ecological interactions with Southern Redbelly Dace and Redbreast Sunfish to evaluate potential risks posed by these species. Document any spatial and temporal overlap in resources used by the two dace species at disturbed and relatively undisturbed sites. • Evaluate the significance of Beaver colonization in Blackside Dace watersheds and quantify the degree of threat associated with this activity. • Monitor the success of habitat improvement and stream restoration projects to better understand what features of restoration appear to offer the most benefit to Blackside Dace. • Produce a developmental series of Blackside Dace early life-history stages to facilitate identification and to better understand the pace of morphological maturation in young Blackside Dace. Study early life-history stages to mark milestones such as first exogenous feeding events, determine dietary and habitat preferences, and document the onset of other key behaviors. Predict if and when ontogenetic niche shifts would occur in a natural setting. We also offer the following suggestions for management and recovery of Blackside Dace populations. The constructive working relationships developed among the biologists, landowners, private businesses, regulatory agencies, and others during the past few decades should serve as a springboard for progress on future recovery efforts. 187 H.T. Mattingly and M.A. Floyd 2013 Southeastern Naturalist Vol. 12, Special Issue 4 • Continue to utilize existing legislation and regulations to protect the species and its habitats (e.g., US Endangered Species Act, federal and state surface-mining laws, US Clean Water Act and other water-quality regulations, stream-alteration regulations, Federal Energy Regulatory Commission licensing). • Continue to work cooperatively through habitat conservation plans, Farm Bill programs, Partners for Fish and Wildlife program projects, state stream mitigation programs, and other resources to address non-pointsource pollution and to protect, enhance, and restore dace populations and their habitats. • Develop a range-wide conservation strategy (a strategic plan that identifies the species’ threats and guides conservation efforts designed to ameliorate those threats) for Blackside Dace and other imperiled fishes such as Cumberland Arrow Darter and Cumberland Darter in the upper Cumberland River drainage. • Revise the Blackside Dace recovery plan (USFWS 1988) to reflect (1) the best available scientific information regarding the species’ biology and threats and (2) the goals and objectives identified in the conservation strategy defined in the suggestion immediately above. • Initiate other recovery actions as specified in the conservation strategy and recovery plan (USFWS 1988). In conclusion, the species continues to face a variety of threats across its range, but we are optimistic about the future prospects for Blackside Dace conservation. A number of federal and state agencies, conservation groups, and private citizens have worked cooperatively and successfully on recovery activities for the species. We expect this cooperation and progress to continue. Much has been learned about the species since its formal description, as noted by Starnes (2013) in the Foreword, but information is sparse or lacking on several research topics identified in this essay. We look forward to observing steady research and management progress in upcoming years, and we heartily invite the participation of others in our collaborative venture to preserve this “exquisite little fish” for future generations. Acknowledgments We thank The Nature Conservancy (Tennessee Chapter) for sponsoring the page charges associated with this article. The manuscript was improved by comments from several other authors in this volume. Disclaimer The findings and conclusions in this article are those of the authors and do not necessarily represent the views of the US Fish and Wildlife Service. H.T. Mattingly and M.A. Floyd 2013 Southeastern Naturalist 188 Vol. 12, Special Issue 4 Literature Cited Bivens, R.D., B.D. Carter, C.E. Williams, E.M. Scott, Jr., D.E. Stephens, V.R. Bishop, and H.T. Mattingly. 2013. New occurrence records of Blackside Dace, Chrosomus cumberlandensis, in the Big South Fork Cumberland River drainage. Southeastern Naturalist 12 (Special Issue 4):171–175. Black, T.R., J.E. Detar, and H.T. Mattingly. 2013a. Population densities of the threatened Blackside Dace, Chrosomus cumberlandensis, in Kentucky and Tennessee. Southeastern Naturalist 12 (Special Issue 4):6–26. Black, T.R., B.K. Jones, and H.T. Mattingly. 2013b. Development and validation of habitat models for the threatened Blackside Dace, Chrosomus cumberlandensis, at two spatial scales. Southeastern Naturalist 12 (Special Issue 4):27–48. Compton, M.C., M.A. Floyd, and D.E. Stephens. 2013. Changes in fish community structure and effects on Blackside Dace (Chrosomus cumberlandensis) populations following beaver colonization in Davis Branch, Cumberland Gap National Historic Park, Bell County, Kentucky. Southeastern Naturalist 12 (Special Issue 4):112–128. Detar, J.E., and H.T. Mattingly. 2013. Movement patterns of the threatened Blackside Dace, Chrosomus cumberlandensis, in two southeastern Kentucky watersheds. Southeastern Naturalist 12 (Special Issue 4):64–81. Eisenhour, D.J., and M.A. Floyd. 2013. A culvert acts as a barrier for Blackside Dace (Chrosomus cumberlandensis) movements in Lick Fork, Kentucky. Southeastern Naturalist 12 (Special Issue 4):82–91. Floyd, M.A., S.L. Harrel, A.C. Parola, C. Hansen, J.B. Harrel, and D.K. Merrill. 2013. Restoration of stream habitat for Blackside Dace, Chrosomus cumberlandensis, in Mill Branch, Knox County, Kentucky. Southeastern Naturalist 12 (Special Issue 4):129–142. Mattingly, H.T., and T.R. Black. 2013. Nest association and reproductive microhabitat of the threatened Blackside Dace, Chrosomus cumberlandensis. Southeastern Naturalist 12 (Special Issue 4):49–63. McAbee, K.T., N.P. Nibbelink, T.D. Johnson, and H.T. Mattingly. 2013. Informing recovery management of the threatened Blackside Dace, Chrosomus cumberlandensis, using a Bayesian-belief network model. Southeastern Naturalist 12 (Special Issue 4):143–161. Papoulias, D.M., and A.L. Velasco. 2013. Histopathological analysis of fish from Acorn Fork Creek, Kentucky, exposed to hydraulic fracturing fluid releases. Southeastern Naturalist 12 (Special Issue 4):92–111. Rakes, P.L., M.A. Petty, J.R. Shute, C.L. Ruble, and H.T. Mattingly. 2013. Spawning and captive propagation of Blackside Dace, Chrosomus cumberlandensis. Southeastern Naturalist 12 (Special Issue 4):162–170. Skelton, C.E. 2013. Distribution of Blackside Dace, Chrosomus cumberlandensis, in the upper Tennessee River drainage of Virginia. Southeastern Naturalist 12 (Special Issue 4):176–180. Starnes, W.C. 2013. Foreword to ecology and conservation of the threatened Blackside Dace, Chrosomus cumberlandensis. Southeastern Naturalist 12 (Special Issue 4):1–3. US Fish and Wildlife Service (USFWS). 1988. Blackside Dace recovery plan. Atlanta, GA. 23 pp.