Part of a series of articles titled Stream Biota Monitoring in the National Capital Region.
Article
Stream Life at Harpers Ferry National Historical Park
U.S. National Park Service
Scientists working with the National Capital Region Inventory & Monitoring Network (NCRN I&M) monitor the health of fish and macroinvertebrate communities in Flowing Springs Run at Harpers Ferry National Historical Park. They assess stream fish and macroinvertebrates using the Fish Index of Biotic Integrity and the Benthic Index of Biotic Integrity. These scoring systems take into account the number of taxa; abundance of individuals; and the proportion of taxa that are sensitive, intermediate, or tolerant to disturbance; as well as comparisons with biological communities expected in environments like Harpers Ferry's. Scientists also collect data on the physical characteristics of these streams to assess the habitat they provide.
Harpers Ferry sits in the Blue Ridge Mountains, and this mountainous terrain is mostly made up of metamorphic rock. Falling within the floodplains of the Potomac and Shenandoah Rivers, roughly 70% of the park’s land is covered with eastern deciduous forest. Most of the Flowing Springs Run watershed lies outside of park boundaries.
Fish Community
Emilio Concari (CC BY-NC)
Fish Index of Biotic Integrity
Harpers Ferry's Flowing Springs Run received a Fish Index of Biotic Integrity (FIBI) score of 3.7 (fair) in 2022, and monitoring shows a steady improvement in this score over the last two decades.
FIBI scores use data such as the abundance of fish that are disturbance tolerant, insect-eating, omnivorous, or benthic to assess stream health. Scores range from 1 to 5, with four possible ratings: very poor (1–1.99), poor (2–2.99), fair (3–3.99), and good (4–4.99). Figure 1 shows FIBI scores for Flowing Springs Run.
Fish Index of Biotic Integrity ranges from 1 to 5. Gray bars indicate 2013 data, while white bars show data from 2022. The background of the bar plots is split into four differently shaded regions based on the score categories described in the figure caption.
Species Found
In 2022, six species of fish were observed in Flowing Springs Run, similar to the previous monitoring cycle. Two of those species, the river chub and the central stoneroller, are considered sensitive to environmental degradation. River chub (Nocomis micropogon) was the most abundant fish species observed in the stream, with 97 individuals.
U.S. National Park Service
The number of river chub recorded at the stream increased considerably since 2013 (from 4 to 97 individuals), while the abundance of longnose dace remained fairly steady. One game fish species, the largemouth bass (Micropterus salmoides), was observed in 2022 (one individual), whereas none were recorded in 2013.
Flowing Springs Run Fish Species
2022 FIBI: 3.7 (fair)
| Species | # of Individuals |
|---|---|
| River chub (Nocomis micropogon) | 97 |
| Longnose dace (Rhinichthys cataractae) | 43 |
| Greenside darter (Etheostoma blennioides) | 5 |
| Yellow bullhead (Ameiurus natalis) | 2 |
| Largemouth bass (Micropterus salmoides)* | 1 |
| Central stoneroller (Campostoma anomalum) | 1 |
*Game fish
Macroinvertebrate Community
Like fish, macroinvertebrates are water quality indicators. Some taxa, such as certain types of dragonflies, worms, and non-biting midges, can tolerate poor environmental conditions. Others, including mayflies, stoneflies, and caddisflies, are more sensitive to higher temperatures and pollution levels.
In addition, macroinvertebrates are a major food source for other aquatic animals. Most fish would not be able to survive without them.
© David H. Funk. / Stroud Water Research Center
Benthic Index of Biotic Integrity
Similar to the previous monitoring cycle in 2013, Flowing Springs Run received a Benthic Index of Biotic Integrity (BIBI) score of 1.44, which is considered very poor.
Like FIBI, BIBI scores are used to evaluate stream health and take into account the tolerance and abundance of macroinvertebrate taxa, as well as the way each organism feeds and its habitat. BIBI scores range from 1 to 5, with four possible ratings: very poor (1–1.99), poor (2–2.99), fair (3–3.99), and good (4–4.99). Figure 2 shows BIBI scores for Flowing Springs Run.
Benthic Index of Biotic Integrity ranges from 1 to 5. Gray bars indicate 2013 data, while white bars show data from 2022. The background of the bar plots is split into four differently shaded regions based on the score categories described in the figure caption.
Taxa Found
In 2022, 23 benthic (bottom-dwelling) macroinvertebrate taxa were observed at Flowing Springs Run, consistent with 2013 monitoring data. Lirceus (isopods, intermediate sensitivity) was the most commonly identified taxon, accounting for 25.7% of macroinvertebrates recorded at the stream. Lirceus was not found at the stream in 2013. Orthocladius, which only accounted for less than three percent of individuals recorded in 2013, made up 19.4% of macroinvertebrates in 2022.
Parakiefferiella, a sensitive genus of non-biting midges, also increased in relative abundance from nearly six percent of recorded individuals to 17.8%. Although not reflected in the BIBI score, this increase in a sensitive taxon might indicate an improvement in stream health.
Flowing Springs Run Top 5 Most Common Macroinvertebrate Taxa
Table shows five most common taxa of 23 total found
2022 BIBI: 1.44 (very poor)
| Taxon | % of Total Individuals |
|---|---|
| Lirceus | 25.7 |
| Orthocladius | 19.4 |
| Parakiefferiella* | 17.8 |
| Tvetenia | 8.9 |
| Simulium | 6.3 |
*Sensitive to environmental stress
Stream Physical Habitat Monitoring
Observations of stream physical habitat are gathered at the same location and time as macroinvertebrate monitoring in spring and fish monitoring in late summer. The physical habitat characteristics fall into two broad categories: solid substrates (stream bed materials), and stream flow and depth.
Solid Substrates
- Embeddedness of substrates: higher embeddedness = less available habitat for small fish, macroinvertebrates, and periphyton (small surface-growing organisms)
- Epifaunal substrate: the amount and variety of hard materials that can be used as habitat
- Instream habitat quality: higher values = greater variety of habitat and substrate particle sizes
Stream Flow and Depth
- Pool quality: diversity of slow- and still-water habitats. Higher scores = more optimal habitat
- Riffle quality: depth and complexity of riffles (shallow flows disrupted by substrate)
- Water velocity and depth: higher scores indicate greater variety of water speeds and depths
All characteristics except embeddedness of substrates are measured on a scale of 0–20, with 20 being the most optimal habitat conditions. Embeddedness is measured as a percent.
NCRN I&M no longer reports index scores for stream physical habitat but instead provides data on individual measures. These, along with FIBI and BIBI, provide a comprehensive view of stream quality. Other stream physical habitat characteristics observed but not reported here include the quantity of woody debris and root wads in the stream, stream bank stability, percent of channel shaded, distance from nearest road (remoteness), and land cover composition (percent urban, forested, and agricultural land).
Stream habitat quality characteristics at Flowing Springs Run varied (Figure 3). Habitat quality scores increased for Instream habitat, riffle quality, and velocity and depth diversity, and remained the same for epifaunal substrate and pool quality.
Bar plot showing stream physical habitat quality scores, ranging from 0–20, on the y-axis for Flowing Springs Run. Stream physical habitat quality characteristics are listed on the x-axis from left to right as follows: epifaunal substrate, instream habitat, pool quality, riffle quality, velocity/depth. Gray bars indicate data collected in 2013 and white bars indicate data collected in 2022. The background of the bar plots is split into four differently shaded regions based on the habitat quality score categories described in the figure caption.
Although no habitat quality scores declined at Flowing Springs Run, embeddedness increased from 15% in 2013 to 40% in 2022 (Figure 4). Embeddedness, which is closely related to epifaunal substrate, is a measure of habitat availability. An increase in embeddedness indicates less available habitat for stream fish and macroinvertebrates.
A bar plot showing embeddedness at Flowing Springs Run, with 0 percent at the top of the y-axis and 100 percent at the bottom. The bottom region of the graph is shaded red to represent values of 55% or more embedded, which indicate poor stream quality. Values below 55% are considered minimally impaired. Gray bars indicate data collected in 2013 and white bars indicate data collected in 2022.
Conclusions: High FIBI and Low BIBI, Major Increase in Sensitive River Chub
Fish and benthic macroinvertebrate scores tell two different stories of stream quality at Flowing Springs Run. While FIBI was fair and improved from the 2013 score, BIBI remained very poor. The overall increase in fish abundance and presence of sensitive species like river chub may indicate high stream quality. The relative abundance of sensitive midges (Parakiefferiella) also increased, but this did not improve the BIBI score.
Stream physical habitat quality scores generally increased or remained constant. However, the increase in embeddedness may create challenges for aquatic organisms.
Learn More about the National Park Service's Inventory & Monitoring Efforts
To help protect natural resources ranging from bird populations to forest health to water quality, National Park Service scientists perform ecological Inventory & Monitoring (I&M) work in parks across the country. The National Capital Region Network, Inventory & Monitoring program (NCRN I&M) serves national parks in the greater Washington, DC area. Visit the NCRN stream biota monitoring webpage to learn more. Previous cycles of fish, macroinvertebrate, and stream physical habitat monitoring were reported in 2015.
Last updated: December 9, 2025