Part of a series of articles titled Stream Biota Monitoring in the National Capital Region.
Article
Stream Life at National Capital Parks-East
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 at three streams in the parks of National Capital Parks-East (NACE). These include Henson Creek in Suitland Parkway, Still Creek in Greenbelt Park, and Oxon Run in Oxon Cove Park and Oxon Hill Farm. 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 NACE parks. Scientists also collect data on the physical characteristics of these streams to assess the habitat they provide.
NACE parks include Greenbelt Park, Oxon Cove Park and Oxon Hill Farm, Suitland Parkway, and more. These parks fall within the Coastal Plain physiographic province, which is a mostly flat area made up of sediment eroded from the Appalachian Mountains and deposited by various rivers. This region consists of wetlands, forests, valleys, and marshes.
Fish Community
Emilio Concari (CC BY-NC)
Fish Index of Biotic Integrity
Fish Index of Biotic Integrity (FIBI) scores at parks of National Capital Parks-East ranged from fair (Still Creek) to good (Henson Creek and Oxon Run). Since 2013, FIBI increased at Oxon Run, remained the same at Henson Creek and Still Creek.
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 the FIBI scores for each stream site.
A bar plot showing Fish Index of Biotic Integrity, ranging from 1 to 5, on the y-axis, and stream name on the x-axis, listed from left to right as follows: Henson Creek, Oxon Run, and Still Creek. 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 FIBI score categories described in the figure caption.
Species Found
In 2022, 27 species of fish were observed in NACE parks. Species richness remained fairly consistent at the three streams. Oxon Run had the highest fish species richness of the three streams.
U.S. National Park Service
Banded Killifish (Fundulus diaphanus) was the most abundant fish species observed (339 total individuals) but was only found in Oxon Run. The most abundant species in Henson Creek was the redbreast sunfish and in Still Creek was the blacknose dace. Several sensitive fish species were also recorded: central stoneroller, swallowtail shiner, spottail shiner, spotfin shiner, satinfin shiner, rosyside dace, margined madtom, fallfish, and longear sunfish. Central stonerollers were present in all three streams.
The number of game fish found at NACE parks decreased from eight in 2013 to five in 2022, but were found in all three streams (as opposed to just Oxon Run in 2013). Largemouth bass were recorded at Henson Creek and Still Creek, while a smallmouth bass was found at Oxon Run.
Overall fish abundance at each site declined since 2013, especially at Oxon Run. Much of the loss at Oxon Run is in the eastern silvery minnow population, which declined by over one thousand individuals. Other species that have declined at NACE park streams include blacknose dace and tessellated darter, as well as the sensitive swallowtail shiner and satinfin shiner.
Henson Creek Fish Species
2022 FIBI: 4.3 (good)
| Species | # of Individuals |
|---|---|
| Redbreast sunfish (Lepomis auritus) | 152 |
| Central stoneroller (Campostoma anomalum) | 89 |
| Creek chub (Semotilus atromaculatus) | 52 |
| White sucker (Catostomus commersonii) | 38 |
| Tessellated darter (Etheostoma olmstedi) | 38 |
| Swallowtail shiner (Notropis procne) | 27 |
| Green sunfish (Lepomis cyanellus) | 18 |
| Blacknose dace (Rhinichthys atratulus) | 17 |
| American eel (Anguilla rostrata) | 13 |
| Rosyside dace (Clinostomus funduloides) | 9 |
| Satinfin shiner (Cyprinella analostana) | 6 |
| Largemouth bass (Micropterus salmoides)* | 2 |
| Bluegill (Lepomis macrochirus) | 1 |
| Eastern mudminnow (Umbra pygmaea) | 1 |
*Game fish
Species Observed in Oxon Run
2022 FIBI: 4.3 (good)
| Species | # of Individuals |
|---|---|
| Banded killifish (Fundulus diaphanus) | 339 |
| E. silvery minnow (Hybognathus regius) | 183 |
| Mummichog (Fundulus heteroclitus) | 141 |
| American eel (Anguilla rostrata) | 97 |
| Eastern mosquitofish (Gambusia holbrooki) | 56 |
| Redbreast sunfish (Lepomis auritus) | 48 |
| Tessellated darter (Etheostoma olmstedi) | 32 |
| Central stoneroller (Campostoma anomalum) | 6 |
| Largemouth bass (Micropterus salmoides) | 5 |
| Blacknose dace (Rhinichthys atratulus) | 3 |
| Greenside darter (Etheostoma blennioides) | 2 |
| Yellow bullhead (Ameiurus natalis) | 1 |
| White sucker (Catostomus commersonii) | 1 |
| Smallmouth bass (Micropterus dolomieu)* | 1 |
| Longear sunfish (Lepomis megalotis) | 1 |
| Bluegill (Lepomis macrochirus) | 1 |
*Game fish
Species Observed at Still Creek
2022 FIBI: 3.7 (fair)
| Species | # of Individuals |
|---|---|
| Blacknose dace (Rhinichthys atratulus) | 75 |
| Tessellated darter (Etheostoma olmstedi) | 66 |
| American eel (Anguilla rostrata) | 59 |
| Longnose dace (Rhinichthys cataractae) | 51 |
| Creek chub (Semotilus atromaculatus) | 27 |
| Spottail shiner (Notropis hudsonius) | 11 |
| Swallowtail shiner (Notropis procne) | 5 |
| Central stoneroller (Campostoma anomalum) | 3 |
| White sucker (Catostomus commersonii) | 3 |
| Margined madtom (Noturus insignis) | 3 |
| Spotfin shiner (Cyprinella spiloptera) | 2 |
| Largemouth bass (Micropterus salmoides)* | 2 |
| Fallfish (Semotilus corporalis) | 2 |
| Eastern mudminnow (Umbra pygmaea) | 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
Henson Creek had the highest Benthic Index of Biotic Integrity (BIBI) score at a National Capital Parks-East park with 2.56 (poor), a slight decrease from 2013. BIBI decreased to 1.37 (very poor) at Oxon Run, and 2.37 (poor) at Still Creek.
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 the BIBI scores for each stream site.
A bar plot showing Benthic Index of Biotic Integrity, ranging from 1 to 5, on the y-axis, and stream name on the x-axis, listed from left to right as follows: Henson Creek, Oxon Run, and Still Creek. 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 BIBI score categories described in the figure caption.
Taxa Found
In 2022, 35 benthic (bottom-dwelling) macroinvertebrate taxa were observed across three stream sites. Taxa richness increased slightly at Henson Creek but declined at Oxon Run and Still Creek.
Cricotopus, a tolerant genus of non-biting midges, was the most commonly identified taxon at the park, accounting for 34.1% of macroinvertebrates. Cricotopus was most dominant at Oxon Run, which had the lowest BIBI score, and increased in relative abundance at all three streams. All of the most common taxa at NACE parks were intermediate or tolerant of environmental disturbance.
Macroinvertebrate communities at some sites have shifted since 2013. Three of the five most common taxa at Henson Creek—Hydrobaenus, Oligochaeta, and Rhecricotopus—were recorded for the first time at the stream in 2022. Likewise, Cardiocladius and Dicrotendipes were found for the first time at Still Creek in 2022.
Henson Creek Top 5 Most Common Macroinvertebrate Taxa
Table shows five most common taxa of 24 total found
2022 BIBI: 2.56 (poor)
| Taxon | % of Total Individuals |
|---|---|
| Cricotopus | 15.2 |
| Hydrobaenus | 14.0 |
| Oligochaeta | 13.4 |
| Orthocladius | 10.4 |
| Rheocricotopus | 10.4 |
Oxon Run Top 5 Most Common Macroinvertebrate Taxa
Table shows five most common taxa of 12 total found
2022 BIBI: 1.37 (very poor)
| Taxon | % of Total Individuals |
|---|---|
| Cricotopus | 59.2 |
| Orthocladius | 26.2 |
| Polypedilum | 6.3 |
| Cardiocladius | 2.1 |
| Dicrotendipes | 1.0 |
Still Creek Top 5 Most Common Macroinvertebrate Taxa
Table shows five most common taxa of 22 total found
2022 BIBI: 2.37 (poor)
| Taxon | % of Total Individuals |
|---|---|
| Cricotopus | 25.4 |
| Polypedilum | 24.9 |
| Hydrobaenus | 11.9 |
| Orthocladius | 6.7 |
| Tanytarsus | 5.7 |
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, which is closely related to epifaunal substrate, indicates habitat availability and 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 physical habitat characteristic scores were marginal or suboptimal at all three streams in National Capital Parks-East parks (Figure 3). Change in scores over time varied widely; all streams improved in some characteristics and declined in others.
Embeddedness, which is closely related to epifaunal substrate, is a measure of habitat availability. Embeddedness increased at Henson Creek and Oxon Run, and decreased at Still Creek, indicating greater habitat availability (Figure 4). At Oxon Run, embeddedness rose above 55%, which some fish and macroinvertebrates may not be able to tolerate.
Three bar plots showing stream physical habitat quality scores, ranging from 0–20, on the y-axis for Henson Creek, Oxon Run, and Still Creek. 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.
A bar plot showing embeddedness as a percent at National Capital Parks-East streams, 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. Streams are listed on the x-axis as follows: Henson Creek, Oxon Run, Still Creek. Gray bars indicate data collected in 2013 and white bars indicate data collected in 2022.
Conclusions: Healthy Fish Communities, Macroinvertebrate Communities and Stream Habitat Characteristics Vary
Fish communities at NACE parks were generally healthy, with streams receiving good (Henson Creek, Oxon Run) or fair (Still Creek) FIBI scores. Sensitive fish species present at each stream may indicate high water quality. However, BIBI scores and stream physical habitat characteristics varied. Oxon Run, which had a higher FIBI score in 2022 than 2013, had the lowest BIBI score and highest embeddedness percentage, which could be a sign of declining stream quality. Henson Creek had healthy fish communities but scored lower than the other streams in multiple habitat characteristics.
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 2014 and 2015.
Last updated: November 18, 2025