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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 - HMattingly@tntech.edu.
Ecology and Conservation of the Threatened Blackside Dace, Chrosomus cumberlandensis
2013 Southeastern Naturalist 12(Special Issue 4):181–188
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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.
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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.
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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
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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
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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.
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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.
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