Catoctin Mountain Water Temperature Study
Prepared by Andrew Sarcinello, NCC-TU Conservation Chair, in April 2022. The version below is abbreviated from the original report. For a PDF of the full report, please use the link below.
| catoctin_mountain_water_temperature_study.pdf |
PROJECT ORIGINS
In summer 2020, NCC-TU monitored water temperature at 32 sites across four Catoctin Mountain watersheds. All sites monitored are known to support native brook trout populations ranging from stable populations comprised of hundreds of fish to marginal populations sustained only by a few spawning pairs of adult fish in the entire stream. NCC-TU hoped the data obtained would offer insights into the resilience of these native trout populations to the predicted warming effects of climate change and help Trout Unlimited identify areas that might present opportunities for future projects to reduce water temperatures or otherwise strengthen the resilience of these populations to warming conditions.
Above: A native brook trout from a Catoctin Mountain stream.
WHY BROOK TROUT?
The plight of brook trout in Maryland (and in many states across the eastern U.S.) has been well documented: man-made disturbances to the natural environment in the form of development, agriculture, and introduction of non-native fish species (brown and rainbow trout) have reduced the occupied range of brook trout to a tiny fraction of the historical range.
In 2019, Freshwater Fisheries staff with Maryland Department of Natural Resources (DNR) presented the results of a five-year electrofishing study of all known brook trout streams in the state. DNR found that the number of streams inhabited by brook trout has declined by over 20% since serious study first began in the early 1980s. The rate of extirpation of Catoctin Mountain populations closely followed the statewide average, with lesser declines in far western MD and a dramatic 49% decline observed in central MD’s piedmont region.
STUDY DESIGN
NCC-TU scoped the study geographically to complement work previously performed by Dr. Hitt’s team at USGS a few years prior – that study focused on brook trout streams only on Catoctin Mountain National Park land. NCC-TU focused on obtaining data in 4 other sub-watersheds outside of the National Park, with most sites being located on land owned by the State Park, City of Frederick, and a handful of sites on private land (where permission was obtained to conduct the research). To protect sensitive areas and to keep the results out of internet search engines, the specific names of these streams will not be provided in this public report, though people who are familiar with the area can probably figure out which streams were studied from the map below.
The plight of brook trout in Maryland (and in many states across the eastern U.S.) has been well documented: man-made disturbances to the natural environment in the form of development, agriculture, and introduction of non-native fish species (brown and rainbow trout) have reduced the occupied range of brook trout to a tiny fraction of the historical range.
In 2019, Freshwater Fisheries staff with Maryland Department of Natural Resources (DNR) presented the results of a five-year electrofishing study of all known brook trout streams in the state. DNR found that the number of streams inhabited by brook trout has declined by over 20% since serious study first began in the early 1980s. The rate of extirpation of Catoctin Mountain populations closely followed the statewide average, with lesser declines in far western MD and a dramatic 49% decline observed in central MD’s piedmont region.
STUDY DESIGN
NCC-TU scoped the study geographically to complement work previously performed by Dr. Hitt’s team at USGS a few years prior – that study focused on brook trout streams only on Catoctin Mountain National Park land. NCC-TU focused on obtaining data in 4 other sub-watersheds outside of the National Park, with most sites being located on land owned by the State Park, City of Frederick, and a handful of sites on private land (where permission was obtained to conduct the research). To protect sensitive areas and to keep the results out of internet search engines, the specific names of these streams will not be provided in this public report, though people who are familiar with the area can probably figure out which streams were studied from the map below.
Above: Map showing the locations where water temperature data was successfully obtained during this study. The project volunteers covered a lot of ground and spent many hours installing and later retrieving the equipment.
FINDINGS
The water temperature data collected revealed some incredibly useful information. From the 2020 data, NCC-TU captured:
The water temperature data collected revealed some incredibly useful information. From the 2020 data, NCC-TU captured:
- Severe negative thermal impacts below ponds and lakes
- Areas of groundwater recharge and thermal refuge
- Impacts of road runoff
- Coldest water temperatures correlate to the strongest brook trout populations
- Every degree of warming increases the severity of impacts on brook trout range in Catoctin Mountain streams: 1 deg C increase may not produce noticeable impacts, but 3 degrees would be severe.
- Even a 3-degree increase would not eliminate brook trout from Catoctin Mountain.
- As water temperature increases, brook trout populations will become less dense and potentially more isolated (even more so than they already are).
HOW TU CAN HELP
The 2020 summer water temperature study illustrates several ways that Trout Unlimited can work to protect brook trout in Catoctin Mountain against the projected impacts of climate warming:
ACKNOWLEDGEMENTS
NCC-TU could not have implemented this important water temperature study without help from many organizations and individuals. We would like to thank:
This project was a true team effort, and we greatly appreciate the contributions of everybody involved. Thank you!
The 2020 summer water temperature study illustrates several ways that Trout Unlimited can work to protect brook trout in Catoctin Mountain against the projected impacts of climate warming:
- Ensure fish can freely migrate to areas of coldwater refuge. NCC-TU has already identified a site on one studied stream where a diverted tributary mouth into an unnatural channel (an old road bed/current mountain biking trail) makes it difficult for brook trout to move from the warmer main stem into the colder tributary. Addressing the issue at this particular site will require coordination with the City of Frederick and local trail user groups.
- Monitor the brook trout watersheds for proposed land use changes that may degrade the habitat conditions in the critical thermal refuge stream sections. Fish accessing the coldest water is one thing, but there must also be deep water and cover to hide from predators within those cold trickles. Land clearing for houses or other construction contributes to siltation of in-stream habitat, and increased flood flows which can push important woody debris out of the stream channel and onto the banks.
- Push for removal of defunct pond dams and oppose construction of new ponds in brook trout watersheds.
- Encourage the cessation of stocking over native brook trout populations, where it is still occurring. Given the predictions of increased stress on brook trout in the future, stocked trout represent nothing besides competition for dwindling habitat and are potential vectors for disease transmission to stressed native trout.
- Support projects that reduce stormwater runoff from existing paved and gravel roadways. MD DNR and the City of Frederick are already engaged in discussions to address road runoff on city-owned property.
- Initiate projects to establish riparian buffers to shade and cool brook trout streams. Fortunately, most of the Catoctin Mountain brook trout streams are already fully forested, so there are not many riparian buffer opportunities here.
- Monitor current populations of mixed brook and brown trout streams for population shifts in favor of brown trout. Additionally, monitor brook trout only streams for introduction/natural establishment of non-native brown trout. Brown trout are more tolerant of warm water and siltation than brook trout. They replace brook trout over time by outcompeting brook trout during stressful conditions.
- As anglers, avoid fishing these brook trout streams whenever water temperatures consistently exceed 65 degrees F. Trout that are caught and released during warm water temperatures are susceptible to dying afterward, as their bodies are subjected to more stress than they would otherwise be if left alone. Based on the 2020 data, this period occurs in most streams between the middle of June and middle of July and lasts until the middle to end of August.
ACKNOWLEDGEMENTS
NCC-TU could not have implemented this important water temperature study without help from many organizations and individuals. We would like to thank:
- Patagonia for providing the grant funding used to purchase the temperature monitoring equipment.
- Maryland DNR Freshwater Fisheries and Dr. Nathaniel Hitt with USGS for their early guidance and influence on the study design and for helping arrange access to a few restricted areas.
- All of the volunteers (NCC-TU members and non-members alike) who supported the project with volunteer hours spent constructing protective housing, providing tools for the installation, and for spending hours hiking through the rugged Catoctin Mountain terrain to successfully reach the installation locations.
- The NCC-TU Board for agreeing to undertake and support this unique project.
This project was a true team effort, and we greatly appreciate the contributions of everybody involved. Thank you!
| catoctin_mountain_water_temperature_study.pdf |