Stream Life at Catoctin Mountain Park

Blue Blazes Creek at Catoctin Mountain Park.

U.S. National Park Service

Key Points

• Stream biota was monitored at Catoctin in 2022 during the 2019–2022* monitoring cycle.
• Fish Community ranged from fair to good. Ten species of fish were observed across three stream sites. 
• Macroinvertebrate Community was in poor to fair condition, depending on the stream. Forty-six aquatic macroinvertebrate taxa were observed. 
• Stream Physical Habitat characteristics were mostly suboptimal or marginal and varied by stream. 

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

Stream monitoring locations at Catoctin.

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 Catoctin Mountain Park. These include Owens Creek, Big Hunting Creek, and Blue Blazes Creek (previously called Whiskey Still Creek). 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 Catoctin's. Scientists also collect data on the physical characteristics of these streams to assess the habitat they provide.

Catoctin falls within the Blue Ridge physiographic province, which is a highly mountainous stretch of metamorphic rock. The park is predominantly covered in Eastern Deciduous Forest.

Fish Community

Blacknose dace is a highly abundant species in Catoctin streams.

U.S. National Park Service

Fish Index of Biotic Integrity 

Fish Index of Biotic Integrity (FIBI) scores at Catoctin Mountain Park ranged from fair (Blue Blazes Creek) to good (Big Hunting Creek and Owens Creek). FIBI improved from the previous monitoring year at all streams, especially at Blue Blazes Creek, where no fish were recorded in 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 three streams at Catoctin Mountain Park. 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 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: Big Hunting Creek, Blue Blazes Creek, and Owens 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

In 2022, ten species of fish were observed in Catoctin across the three stream sites. Blacknose dace (Rhinichthys atratulus) was the most abundant fish species observed (802 total individuals). Blacknose dace and Blue Ridge sculpin were recorded at all streams and increased in abundance at Big Hunting Creek and Owens Creek. Seventy-four game fish of three different trout species were observed at Catoctin: brook trout (the only native trout), brown trout, and rainbow trout (an increase from the 39 game fish recorded in 2010).

Fish counts were highest at Owens Creek and lowest at Blue Blazes Creek. Big Hunting Creek, which had the highest FIBI score, had the highest species richness (eight species).

Big Hunting Creek Fish Species
2022 FIBI: 4.7 (good)

Species	# of Individuals Observed
Blue Ridge sculpin (Cottus caeruleomentum)	196
Blacknose dace (Rhinichthys atratulus)	138
Longnose dace (Rhinichthys cataractae)	31
Brown trout (Salmo trutta)*	23
Fantail darter (Etheostoma flabellare)	14
White sucker (Catostomus commersonii)	2
Banded killifish (Fundulus diaphanus)	2
Rainbow trout (Oncorhynchus mykiss)*	1

*Game fish

Blue Blazes Creek Fish Species
2022 FIBI: 3.3 (fair)

Species	# of Individuals Observed
Blacknose dace (Rhinichthys atratulus)	190
Blue Ridge sculpin (Cottus caeruleomentum)	34
Brown trout (Salmo trutta)*	4

*Game fish

Owens Creek Fish Species
2022 FIBI: 4.3 (good)

Species	# of Individuals Observed
Blacknose dace (Rhinichthys atratulus)	474
Blue Ridge sculpin (Cottus caeruleomentum)	333
Brook trout (Salvelinus fontinalis)*	46
Fantail darter (Etheostoma flabellare)	43
Creek chub (Semotilus atromaculatus)	15
Longnose dace (Rhinichthys cataractae)	5

*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.

Larval midges in the Chironomidae family, which includes the genus Sympotthastia, the most abundant macroinvertebrate taxon at Catoctin.

© David H. Funk. / Stroud Water Research Center

A juvenile mayfly in the Ephemerellidae family, which includes the genus Ephemerella, a common taxon at Catoctin.

© David H. Funk. / Stroud Water Research Center

Benthic Index of Biotic Integrity

Catoctin streams had Benthic Index of Biotic Integrity (BIBI) scores of fair (Big Hunting Creek, Owens Creek) or poor (Blue Blazes Creek). BIBI scores at all three sites decreased since 2010.

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 three streams at Catoctin Mountain Park. 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: Big Hunting Creek, Blue Blazes Creek, and Owens 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, 46 benthic (bottom-dwelling) macroinvertebrate taxa were observed across three stream sites at Catoctin. Tolerant Sympotthastia (a non-biting midge), found in all three streams, was the most commonly identified taxon in 2022, accounting for 66.1% of all macroinvertebrates recorded at the park. In 2010, Baetis (mayflies, intermediate sensitivity) was the most common taxon at the park, constituting about 10.9% of individuals recorded. Sympotthastia were most common at Blue Blazes Creek and Owens Creek, while Ephemerella, a genus of mayflies that is sensitive to environmental conditions, was the most abundant at Big Hunting Creek. Other sensitive taxa found at Catoctin include Prosimulium (black flies), Oulimnius (beetles), and Epeorus (mayflies).

Overall, pollution-tolerant macroinvertebrate taxa outnumbered the sensitive taxa, especially at Blue Blazes Creek, where Sympotthastia were dominant despite never having been recorded previously at the stream. In 2010, the most common taxon at Blue Blazes Creek was Epeorus, which accounted for 18.5% of all macroinvertebrates found in the stream.

Big Hunting Creek Top 5 Most Common Macroinvertebrate Taxa
Table shows five most common taxa of 26 total found
2022 BIBI: 3.37 (fair)

Species	% of Total Individuals
Ephemerella*	38.7
Prosimulium*	24.1
Baetis	8.0
Orthocladius	5.0
Epeorus*	3.5

*Sensitive to environmental stress

Blue Blazes Creek Top 5 Most Common Macroinvertebrate Taxa
Table shows five most common taxa of 23 total found
2022 BIBI: 2 (poor)

Species	% of Total Individuals
Sympotthastia	83.2
Prosimulium*	6.7
Ephemerella*	4.3
Oulimnius*	1.3
Epeorus*	0.9

*Sensitive to environmental stress

Owens Creek Top 5 Most Common Macroinvertebrate Taxa
Table shows five most common taxa of 27 total found
2022 BIBI: 3.13 (fair)

Species	% of Total Individuals
Sympotthastia	29.1
Ephemerella*	24.6
Orthocladius	11.6
Oulimnius*	7.5
Baetis	4.5

*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 Catoctin (Figure 3). Big Hunting Creek had the highest habitat scores across the board. Blue Blazes Creek, which had the lowest FIBI and BIBI scores, generally had lower habitat quality scores compared to the other two streams. Although Blue Blazes Creek had low habitat quality scores, scores improved since 2010.

Figure 3. Stream physical habitat characteristics of Catoctin 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. A dot indicates a zero score.

Narrative figure description

Three bar plots showing stream physical habitat quality scores, ranging from 0–20, on the y-axis for Big Hunting Creek, Blue Blazes Creek, and Owens 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.

Embeddedness, which is closely related to epifaunal substrate, is a measure of habitat availability. Embeddedness at Big Hunting Creek and Blue Blazes Creek was less than 55%, which indicates greater habitat availability and is considered sufficient for most fish and macroinvertebrates. Ownes Creek, however, had an embeddedness of 60%, which some species may not be able to tolerate.

Figure 4. Embeddedness at Catoctin 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 Catoctin 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: Big Hunting Creek, Blue Blazes Creek, Owens Creek. Gray bars indicate data collected in 2010 and white bars indicate data collected in 2022. 

Conclusions on Stream Life at Catoctin

Fish Communities are Healthy, Non-Native Game Fish Increase

Fish communities in Catoctin streams indicate fair to good stream health. FIBI increased at all three streams. Consistent with the prior monitoring year, blacknose dace was the most abundant fish species, followed by Blue Ridge sculpin. The overall number of fish recorded increased, including the number of non-native game fish.
As of 2022, native brook trout were present in Owens Creek, but were not detected in Big Hunting or Blue Blazes Creeks.

Presence of Sensitive Macroinvertebrates at Blue Blazes Creek Overshadowed by Tolerant Taxa

The number of aquatic macroinvertebrates recorded at each stream increased, but the number of taxa decreased. The greatest decline in BIBI occurred at Blue Blazes Creek. While multiple sensitive macroinvertebrate taxa are present in Blue Blazes Creek, one tolerant taxon, Sympotthastia, dominated the stream, accounting for about 83% of all macroinvertebrates recorded. This drastic population increase may indicate deteriorating stream quality. Owens Creek has also experienced an increase in the proportion Sympotthastia, although to a lesser extent.

Stream Physical Habitat Quality Varies

Big Hunting Creek had the most favorable stream physical habitat characteristics of the three streams but, along with Owens Creek, scored lower in most categories compared to 2010. All stream physical habitat variables aside from embeddedness improved at Blue Blazes Creek.

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.