Upper Little Tennessee River · HUC 06010202
He came to the mountains for a fish with no name.
The Smoky Dace has never been formally described — no species name, no type specimen. It is nonetheless counted among the sensitive species used to grade stream health across western North Carolina. That designation was made when far less was known about the fish. Seventeen streams and three decades of biomonitoring now offer enough evidence to revisit it.
Specimen tagULT / Leuciscidae
Clinostomus sp.
“Smoky” Dace · undescribed
RangeUpper Little T. & Tuckasegee
NC statusSpecial concern
Trophic guildSpecialized insectivore
Basis of designationInherited
IntolerantTolerance categories
How a fish comes to stand for the health of a stream
Some fish species can be used as biological indicators of stream health. Indicator species are generally placed into 2 categories: intolerant species that are sensitive to pollution and other stressors, and tolerant species that are resilient and sometimes thrive under degraded conditions.
An example of a sensitive species is Brook Trout, a species that thrives only in clear, cold streams in our region. An example of a species that is not sensitive to pollution is the Creek Chub, a widespread species that can be found in degraded streams.
The designated species
Fig. 01 · select a speciesThe 14 designated taxa among the 36 sampled in 2024, with trophic guild, as used in McLarney’s Upper Little Tennessee IBI (Alvis et al. 2026, supplemental Table 5). The other 22 taxa sampled carry no tolerance designation and sit outside this framework. The Smoky Dace entry was carried over from the Rosyside Dace, Clinostomus funduloides, rather than derived from local data. Filling that gap is what this study set out to do.
As an endemic species with a narrow geographical range, the Smoky Dace has been classified as a sensitive species, intolerant of pollution and other stressors. Its sister species, the Rosyside Dace, which is also classified as a sensitive species, declines in numbers when waters become filled with silt or otherwise degraded.
Crawford Branch
One stream that did not behave as the designation predicts
However, through his long-term aquatic biomonitoring program, Dr. McLarney has found the Smoky Dace in high numbers in some of the most impaired streams in the upper Little Tennessee River and it is often found alongside another pollution-tolerant species, Creek Chub.
Thirty years of sampling will eventually turn up something the protocol did not anticipate.
Crawford Branch, 2024
Fig. 02 · one site, every metricA low-order urban stream on the EPA’s 303(d) impairment list. Smoky Dace and Creek Chub were the two dominant species there, and 2 of only 7 taxa sampled at the site all year. Smoky Dace was the only nest associate present — Creek Chub builds pit-ridge nests that Clinostomus spawn over, so with no competitors for those nests the dace may have had the run of the place. Its IBI score of 35 places it in the Poor class.
All values from Alvis et al. 2026, Table 2 and Results. SMIE is inverse-scaled — a higher score means worse macroinvertebrate integrity. SVAP runs 1–4, higher is better.
These anecdotal observations led him to question whether the Smoky Dace should be labeled as a pollution intolerant species, observations that Tayton decided to tackle from an analytical perspective.
Seventeen streams
From long-term observation to a measured comparison
Along with additional field work, Tayton used the long-term aquatic biomonitoring data to try and better quantify this phenomenon, to see if perhaps the Smoky Dace has been placed in the wrong category. Tayton surveyed 17 sites in the upper Little Tennessee River system and incorporated environmental metrics like landcover (% forest, % agriculture, % urban, etc.), water quality, and habitat quality to see how these metrics correlated with Smoky Dace density.
The survey network
Fig. 03 · select a streamReal coordinates, catchment areas, index scores and land cover from Table 2; temperature means from Table 8 where loggers were deployed (n = 9). Per-site fish densities were not published, so only the values reported in the Results text are shown. Sites in the Cullasaja, Cowee and Watauga basins were omitted from sampling for lack of Smoky Dace occurrences.
Correlations
What each species’ abundance actually tracks
Tolerant species tend to increase as a stream declines; sensitive species tend to thin out. Spearman rank correlations let us ask which pattern the Smoky Dace follows. Select a species to compare.
Density against stream condition
Fig. 04 · published correlationsCoefficients as published in Alvis et al. 2026 (Results, Figure 2), α = 0.05. Bars are shaded by what the relationship means: tracks degradation, habitat or stream-size preference, or not significant. Variables with no reported significant relationship for a species are omitted, as in the published correlogram.
Community structure
Thirteen years of assemblage data, and where the dace falls within it
Tayton also analyzed the long-term aquatic biomonitoring data from 2010-2022 to see the relationship between fish assemblages (the composition of the fish community) and Index of Biological Integrity (IBI) Scores.
Fish community ordination
Fig. 05 · NMDS, 107 sites, 2010–2022Bray–Curtis dissimilarity, stress = 0.183, 335 sampling events across 107 sites. Intolerant taxa drive site scores positive along NMDS1 and negative along NMDS2; tolerant taxa drive them positive along NMDS2. Smoky Dace sits at the far negative end of NMDS1, beside Creek Chub and Blacknose Dace, and outside the Fair class ellipse — further from the other intolerant species than any of them are from each other.
Species positions digitised from Figure 3 of Alvis et al. 2026; coordinates are read off the published plot and carry small transcription error. Groupings, ellipse placement and the separation of Smoky Dace are as published. Brook Trout does not appear — the dataset was filtered to taxa present in more than 5% of sampling events.
How the index works
Where a tolerance designation enters the calculation
An IBI is not a single measurement. It is a scorecard of metrics, each worth a fixed number of points, added up. These are McLarney’s metrics for the upper Little Tennessee — three versions, because the criteria change with catchment size. Counting intolerant species is one of them, which is why a designation is worth getting right.
IBI metrics, by catchment size
Fig. 06 · McLarney 1995Metrics and scoring criteria from Alvis et al. 2026, supplemental Tables 1–3. Class boundaries: Excellent 58–60, Good 48–55, Fair 39–44, Poor 28–35, Very Poor 12–24 (supplemental Table 4). Because a designation feeds a whole metric rather than a single point, revising a single designation can shift a site’s total by up to 3 points — enough, at some points on the scale, to move it into an adjacent class. Whether that applies at any specific site is not something these published tables can settle, and the paper makes no such claim.
Specimen tagRe-examined 2026
Clinostomus sp.
“Smoky” Dace · undescribed
Correlation with IBINone significant
Correlation with Creek Chubrₛ = 0.52
Ordinal positionOutside Fair class
Endemism → intoleranceNot a safe inference
Intolerant Not supportedWhat it means
Overall, he found that Smoky Dace probably should not be considered a species sensitive to pollution, as they did not meaningfully correlate with any stream health metrics examined, and did not group with other pollution sensitive species.
This research not only provides useful biological information about an as-yet undescribed species but also provides evidence that this endemic species might be placed in the wrong pollution indicator category, which will hopefully help state and federal agencies better refine their IBI scores that will in turn provide a more accurate assessment of stream health.
And that is something that we would all benefit from.
The broader point is about endemism: a narrow geographic range does not by itself make a species a dependable indicator of stream health. And none of this means the Smoky Dace is doing well — it remains a species of special concern in North Carolina, and one of the few the biomonitoring program has recorded declining, having disappeared from streams that once held it. It may be responding to stressors these indices were not built to measure. What the evidence bears on is the designation, not the fish.