Article

Stream Life at Prince William Forest Park

A thin creek full of rocks and covered with tree roots runs through a forest.
Carters Run at Prince William Forest 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 nine streams at Prince William Forest Park. These include Boneyard Run, Carters Run, Mawavi Run, Mary Byrd Branch, North Fork Quantico Creek, Orenda Run, South Fork Quantico Creek, Sow Run, and Taylor Run. 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; the proportion of taxa that are sensitive, intermediate, or tolerant to disturbance; as well as comparisons with biological communities expected in environments like Prince William's. Scientists also collect data on the physical characteristics of these streams to assess the habitat they provide.

Prince William falls within the Coastal Plain and Piedmont physiographic provinces, and contains a large piedmont forest ecosystem.

Map showing location of biological stream survey sites and rivers and streams at Prince William Forest Park.
Stream monitoring locations at Prince William.

Fish Community

A small thin fish with a horizontal black stripe down its body lays against a person’s fingers.
Blacknose dace is a highly abundant species in Prince William streams.

U.S. National Park Service

Fish Index of Biotic Integrity

Fish Index of Biotic Integrity (FIBI) scores varied across Prince William Forest Park streams. Mary Byrd Branch and Sow Run earned 'fair' scores. The remaining sites were either poor or very poor. FIBI improved at four sites—Carters Run, Mary Byrd Branch, Mawavi Run, and North Fork Quantico Creek—since 2011. Carters Run saw the greatest improvement, increasing from 1 (the lowest possible score) in 2011 to 2.3 in 2021. Taylor Run declined from 3 to 1.7.

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 Prince William Forest Park stream name on the x-axis. Refer to narrative figure description for more details.
Figure 1. Fish Index of Biotic Integrity (FIBI) scores for nine streams at Prince William. Scores are measured on a scale of 1 to 5, categorized as: 1–1.99 = very poor, 2–2.99 = poor, 3–3.99 = fair, 4–4.99 = good. Missing bars indicate that the stream was not sampled in that year.

Species Found

Blacknose dace (Rhinichthys atratulus) was the most abundant fish species overall (392 total individuals) and was observed in every stream. Blacknose dace abundance increased at Carters Run and Mawavi Run but decreased at all other sites monitored in both 2011 and 2021.

Multiple sensitive fish species were found at Prince William: rosyside dace, margined madtom, fallfish, cutlips minnow, and common shiner. Sensitive fish were present at all streams except Mawavi Run and Orenda Run, which had two of the lowest FIBI scores. No game fish were recorded.

A small tan fish laying on its side with a horizontal black stripe and a red spot near its gills.
Adult rosyside dace.

U.S. National Park Service

Rosyside dace (a small minnow) increased at Mary Byrd Branch, where the FIBI increased from 2 (poor) to 3 (fair). Rosyside dace were also recorded at Carters Run for the first time in 2022 but were not detected at Mawavi Run, North Fork Quantico Creek, or South Fork Quantico Creek.

Taylor Run, where FIBI decreased from 3 (fair) to 1.7 (very poor), was the only site where fish species richness declined, with ten species observed in 2011 and four in 2021. The common shiner, tessellated darter, pumpkinseed, and river chub were not observed in 2021. Fish abundance also declined at Taylor Run and Orenda Run.

Fish Species Tables

Boneyard Run Fish Species
2021 FIBI: 1.7 (very poor) 

Species # of Individuals Observed
Blacknose dace (Rhinichthys atratulus) 90
American eel (Anguilla rostrata) 9
Rosyside dace (Clinostomus funduloides) 5
Fallfish (Semotilus corporalis) 5
Creek chub (Semotilus atromaculatus) 1

Click panels below to see data for other streams.

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.

A closeup image of an orange-brown insect with a segmented body and a small pair of wings against a rust-colored background
A juvenile stonefly in the Nemouridae family, which includes the most common genus at Prince William (Amphinemura).

© David H. Funk. / Stroud Water Research Center

Benthic Index of Biotic Integrity

Most sites at Prince William Forest Park had Benthic Index of Biotic Integrity (BIBI) scores of poor or fair, except for Mary Byrd Branch and Taylor Run, which were good. BIBI increased at two sites compared to the previous sampling period (Carters Run and Mary Byrd Branch), and decreased at three (Mawavi Run, North Fork Quantico Creek, and Orenda Run).

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 Prince William Forest Park stream names listed on the x-axis. Refer to the narrative figure description for more details.
Figure 2. Benthic Index of Biotic Integrity (BIBI) scores for nine streams at Prince William. Scores are measured on a scale of 1 to 5, categorized as: 1–1.99 = very poor, 2–2.99 = poor, 3–3.99 = fair, 4–4.99 = good. Missing bars indicate that the stream was not sampled in that year.

Taxa Found

In 2021, 63 benthic (bottom-dwelling) macroinvertebrate taxa were observed across nine stream sites. Although the number of taxa decreased at all sites compared to the previous monitoring period in 2011, Prince William had the highest species richness of all national parks monitored for stream biota in the National Capital Region.

Of the most commonly identified macroinvertebrate taxa at each site in Prince William, over half have intermediate sensitivity to environmental conditions, five are sensitive, and one is tolerant.

Amphinemura, a sensitive genus of stoneflies, was the most commonly identified taxon at Prince William, accounting for 15.5% of all macroinvertebrates recorded across the park. These stoneflies were found at every site except North Fork Quantico Creek. While Amphinemura was the most common taxon, it decreased in proportion at all sreams besides Mary Byrd Branch.

Other sensitive taxa also declined. At North Fork Quantico Creek, where BIBI decreased from 4.67 to 2.83, a sensitive genus of caddisflies called Wormaldia was the most common taxon in 2011 but was not recorded at the stream in 2021.

At the same time, the proportion of individuals in the Nemouridae family of stoneflies, which includes Amphinemura, increased since 2011. Nemouridae encompasses multiple genera (plural of genus) that are sensitive to environmental degradation, and one genus that is considered intermediate. At times, it is not possible to identify macroinvertebrates to the genus level; the individuals recorded as Nemouridae may be any one of seven genera. While we do not know the genus of these individuals, it is likely that this increase in Nemouridae indicates an increase in sensitive taxa.

Two prominent taxa, Cricotopus/Orthocladius (non-biting midges, tolerant) and Cnephia (black flies, intermediate), were both recorded for the first time at Prince William in 2021. The proportion of Simulium, a tolerant genus of black flies, increased at multiple sites.

Macroinvertebrate Taxa Tables

Boneyard Run Macroinvertebrate Taxa 
Table shows five most common taxa of 23 total found 
2021 BIBI: 2.78 (poor) 

Taxon % of Total Individuals
Amphinemura* 18.6
Simulium 13.7
Cricotopus/Orthocladius 11.8
Crangonyx 5.9
Eccoptura* 5.9

*Sensitive to environmental stress 

Click panels below to see data for other streams.

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).

South Fork Quantico Creek had the most favorable habitat quality scores, followed by Mary Byrd Branch, Sow Run, and North Fork Quantico Creek, all of which had suboptimal or optimal scores (Figure 3). Orenda Run had some of the lowest scores and declined in several habitat quality metrics since 2011. The streams that had both increased FIBI and BIBI scores, Carters Run and Mary Byrd Branch, also improved in every physical habitat metric.

Nine bar plots showing stream physical habitat quality scores, ranging from 0–20, on the y-axis for nine streams at Prince William Forest Park. Refer to narrative figure description for more information.
Figure 3. Stream physical habitat scores of Prince William streams in 2011 and 2021. Epifaunal substrate, instream habitat, pool quality, riffle quality, and velocity/depth are all measured on a scale of 0–20, categorized as: 0–5 = poor, 6–10 = marginal, 11–15 = suboptimal, 16–20 = optimal. Missing bars indicate that the stream was not sampled in that year.

Embeddedness, which is closely related to epifaunal substrate, is a measure of habitat availability. Embeddedness improved from 2011 to 2021 at all sites that were monitored in both years (Figure 4). Two sites, Carters Run and South Fork Quantico Creek, had an embeddedness of 55%, which is considered too high for some species to tolerate.

A bar plot showing embeddedness as a percent at nine Prince William streams listed along the x-axis, with 0 percent at the top of the y-axis and 100 percent at the bottom. Refer to narrative figure description for more details.
Figure 4. Embeddedness at Prince William streams in 2011 and 2021. Embeddedness is a percent; values of 55% and above indicate less available habitat and poor habitat quality. Missing bars indicate that the stream was not sampled in that year.

Conclusions: Stream Biota Vary, Overall High Macroinvertebrate Diversity, Increases in Sensitive Rosyside Dace

Fish and benthic macroinvertebrate scores and habitat quality varied across Prince William Forest Park streams. The two coastal plain sites, Mary Byrd Branch and Carters Run, had higher FIBI and BIBI scores compared to 2011. However, these scores are not always directly related. For example, North Fork Quantico Creek showed an improvement in FIBI and a considerable decline in BIBI.

Blacknose dace was the most abundant fish species at Prince William. Most fish species found at the park were either tolerant or intermediate. Rosyside dace, one sensitive species recorded this cycle, increased in abundance at Mary Byrd Branch and was recorded for the first time at Carters Run. Most sites where monitoring occurred in both 2011 and 2021 had higher fish species richness.

Amphinemura was the most commonly identified macroinvertebrate taxon. Over half of the most common macroinvertebrate taxa in the park have intermediate sensitivity. Many sites saw increased abundance of tolerant taxa. Mary Byrd Branch and Taylor Run had the highest BIBI scores, while South Fork Quantico Creek and Sow Run had fair scores. The remaining five sites received poor scores.

Stream physical habitat characteristics varied across streams. Mary Byrd Branch and North and South Fork Quantico Creek generally had high stream habitat quality, while Boneyard Run, Mawavi Run, and Orenda Run had lower stream physical habitat quality scores.

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 2012 and 2013.

Part of a series of articles titled Stream Biota Monitoring in the National Capital Region.

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Last updated: November 19, 2025