Stream Life at Monocacy National Battlefield

Bush Creek at Monocacy National Battlefield.

U.S. National Park Service

Key Points

• Stream biota was monitored at Monocacy in 2022 during the 2019–2022* monitoring cycle.  
• Fish Community was fair or good. Twenty-seven species of fish were observed. 
• Macroinvertebrate Community was fair at Gambrill Mill Creek and very poor at Bush Creek. Forty-one aquatic macroinvertebrate taxa were observed across the two stream sites. 
• Stream Physical Habitat characteristics were optimal or suboptimal at Bush Creek and mostly marginal at Gambrill Mill Creek. 

*The previous cycle of this periodic (not annual) monitoring occurred 2008-2014. 

Stream monitoring locations at Monocacy.

Scientists working with the National Capital Region Inventory & Monitoring Network (NCRN I&M) monitor the health of fish and macroinvertebrate communities in three streams at Monocacy National Battlefield. These include Bush Creek and Gambrill Mill Creek. They assessed 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 Monocacy's. Scientists also collect data on the physical characteristics of these streams to assess the habitat they provide.

Monocacy sits within the Piedmont physiographic province, which consists of highly weathered complex metamorphic and igneous rocks. Most of the park is used for agriculture, and a small portion of the park is covered in Eastern Deciduous Forest.

Fish Community

The rainbow darter was the most common fish species observed in Monocacy in 2022.

U.S. National Park Service

Fish Index of Biotic Integrity

Fish Index of Biotic Integrity (FIBI) scores at Monocacy ranged from fair (3.7) at Gambrill Mill Creek to good (4.7) at Bush Creek. FIBI scores at both streams improved slightly since 2010.

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.

Figure 1. Fish Index of Biotic Integrity (FIBI) scores for two streams at Monocacy National Battlefield. 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 a stream was not sampled in that year.

Narrative figure description

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: Bush Creek, Gambrill Mill Creek. Gray bars indicate data collected in 2010 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

Blacknose dace was the most abundant fish species at Gambrill Mill Creek.

U.S. National Park Service

In 2022, 27 species of fish were observed in Monocacy. Although Bush Creek had high fish species richness, the number of species recorded decreased from 27 in 2010 to 23 in 2022. Richness increased at Gambrill Mill Creek from seven species to 11.

Rainbow darter (Etheostoma caeruleum) were the most abundant fish observed at the park (128 total individuals). All rainbow darter were found at Bush Creek, while the most abundant species at Gambrill Mill Creek was the blacknose dace (Rhinichthys atratulus). The abundance of central stoneroller and longnose dace decreased by hundreds of individuals at Bush Creek, and Blue Ridge sculpin declined at both streams.

Two species of game fish were detected in Monocacy, both in Bush Creek: smallmouth bass and rock bass. The total number of game fish recorded at Bush Creek increased from nine in 2010 to 12 in 2022. Multiple sensitive fish species were also recorded at Bush Creek: river chub, rosyface shiner, central stoneroller, fallfish, margined madtom, spotfin shiner, and spottail shiner.

Bush Creek Fish Species

2022 FIBI: 4.7 (good)

Species	# of Individuals
Rainbow darter (Etheostoma caeruleum)	128
Bluntnose minnow (Pimephales notatus)	73
Blue Ridge sculpin (Cottus caeruleomentum)	57
Longnose dace (Rhinichthys cataractae)	57
Greenside darter (Etheostoma blennioides)	54
Fantail darter (Etheostoma flabellare)	50
River chub (Nocomis micropogon)	32
White sucker (Catostomus commersonii)	31
Potomac sculpin (Cottus girardi)	21
Rosyface shiner (Notropis rubellus)	14
Redbreast sunfish (Lepomis auritus)	12
Central stoneroller (Campostoma anomalum)	10
Fallfish (Semotilus corporalis)	10
Smallmouth bass (Micropterus dolomieu)*	7
Tessellated darter (Etheostoma olmstedi)	6
Rock bass (Ambloplites rupestris)*	5
Margined madtom (Noturus insignis)	5
Spotfin shiner (Cyprinella spiloptera)	3
Spottail shiner (Notropis hudsonius)	3
Green sunfish (Lepomis cyanellus)	2
Yellow bullhead (Ameiurus natalis)	1
Bluegill (Lepomis macrochirus)	1
Bluehead chub (Nocomis leptocephalus)	1

*Game fish

Gambrill Mill Creek Fish Species

2022 FIBI: 3.7 (fair)

Species	# of Individuals
Blacknose dace (Rhinichthys atratulus)	116
Fantail darter (Etheostoma flabellare)	31
Green sunfish (Lepomis cyanellus)	9
Blue Ridge sculpin (Cottus caeruleomentum)	7
Eastern mosquitofish (Gambusia holbrooki)	5
Creek chub (Semotilus atromaculatus)	5
White sucker (Catostomus commersonii)	4
Pearl dace (Margariscus margarita)	4
Longnose dace (Rhinichthys cataractae)	3
Potomac sculpin (Cottus girardi)	2
Bluntnose minnow (Pimephales notatus)	1

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.

Larval midges in the Chironomidae family, which includes the genus Orthocladius, the most abundant taxon at Monocacy.

© David H. Funk. / Stroud Water Research Center

Benthic Index of Biotic Integrity

The Benthic Index of Biotic Integrity (BIBI) score at Gambrill Mill Creek increased from poor (2) in 2010 to fair (3.18) in 2022, while BIBI at Bush creek decreased from fair (3) to very poor (1.38).

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.

Figure 2. Benthic Index of Biotic Integrity (BIBI) scores for two streams at Monocacy National Battlefield. 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.

Narrative figure description

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: Bush Creek, Gambrill Mill Creek. Gray bars indicate data collected in 2010 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, 41 benthic (bottom-dwelling) macroinvertebrate taxa were observed across two stream sites. Orthocladius (non-biting midges) was the most commonly identified taxon, accounting for nearly 30% of all macroinvertebrates recorded at the park. Orthocladius was most dominant at Bush Creek, where it made up 59.9% of observations, a major increase from 7.5% in 2010.

A juvenile stonefly in the Nemouridae family, which includes Amphinemura.

© David H. Funk. / Stroud Water Research Center

The taxa found at Gambrill Mill Creek differed from Bush Creek. Amphinemura, a sensitive genus of stoneflies, was most common at Gambrill Mill Creek, followed by Corynoneura, non-biting midges with intermediate sensitivity to environmental disturbance. Three of the five most common taxa at Gambrill Mill Creek—Amphinemura, Corynoneura, and Clinocera—were recorded for the first time at the stream in 2022, signaling a change in community composition from 2010.

Bush Creek Top 5 Most Common Macroinvertebrate Taxa

Table shows five most common taxa of 23 total found
2022 BIBI: 1.38 (very poor)

Taxon	% of Total Individuals
Orthocladius	59.9
Simulium	6.1
Cricotopus	5.6
Thienemanniella	5.6
Clinocera	3.6

Gambrill Mill Creek Top 5 Most Common Macroinvertebrate Taxa

Table shows five most common taxa of 34 total found
2022 BIBI: 3.18 (fair)

Taxon	% of Total Individuals
Amphinemura*	25.4
Corynoneura	18.9
Sympotthastia	7.0
Clinocera	6.0
Hydrobaenus	5.0

*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 varied at Monocacy (Figure 3). Bush Creek had the highest habitat scores across the board. All characteristics at Gambrill Mill Creek were considered marginal, aside from epifaunal substrate.

Embeddedness, which is closely related to epifaunal substrate, is a measure of habitat availability. Embeddedness increased at both sites, indicating less available habitat (Figure 4). At Gambrill Mill Creek, embeddedness rose over 55%, which some fish and macroinvertebrates may not be able to tolerate.

Figure 3. Stream physical habitat characteristics of Monocacy streams in 2010 and 2022. 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.

Narrative figure description

Two bar plots showing stream physical habitat quality scores, ranging from 0–20, on the y-axis for Bush Creek and Gambrill Mill 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 2010 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.

Figure 4. Embeddedness at Monocacy streams in 2010 and 2022. Embeddedness is a percent; values above 55% indicate less available habitat and poor habitat quality.

Narrative figure description

A bar plot showing embeddedness as a percent at Monocacy National Battlefield 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: Bush Creek, Gambrill Mill Creek. Gray bars indicate data collected in 2010 and white bars indicate data collected in 2022. 

Conclusions: Healthy Fish Communities, Diverging BIBI Scores, Variable Habitat Quality

Fish communities at Monocacy indicate good stream health. Bush Creek had high fish species richness and a high FIBI score, while Gambrill Mill Creek had a fair score. While FIBI was good at Bush Creek, a slight decrease in species richness and a declining population of central stoneroller, a sensitive species, may indicate a disturbance in the stream.

Gambrill Mill Creek had a higher BIBI score than Bush Creek, improving from 2 in 2010 to 3.18 in 2022. Despite this, Gambrill Mill Creek had lower stream habitat quality than Bush Creek in every category. At both streams, multiple habitat characteristics declined in quality.

The difference in FIBI, BIBI, and stream physical habitat characteristics at Bush Creek and Gambrill Mill Creek shows that these three components of stream health are not always directly related.

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.