Living on the Edge in the Midst of Change The Challenge to Conserve Eastern Brook Trout

By Tom Champeau, Pisgah Chapter of Trout Unlimited

Eastern brook trout (Salvelinus frontalis) are part of the family Salmonidae that first appeared in the fossil record in the middle Eocene Period (48 to 38 million years ago). Salmonidae diversification into many species was likely driven by multiple glaciation periods that the Earth experienced over several geological ages. Salmonids are widespread in the Northern Hemisphere with 39 known species in North America.

When brook trout (actually a species of charr) diverged from their ancestral lineage is not clear, but it is thought that brook trout appeared in the Southern Appalachians during the Pleistocene (2.5 million to 100,000 years ago). Figure 1 shows the historical and recent (due to stocking in the West) brook trout range. It is likely that brook trout existed in the northern part of their range for millions of years and were distributed by advancing and retreating glaciers which brought them south. The fossil record for brook trout is just too sparse to estimate dates and the maximum extent of their distribution. As the range map shows, brook trout are considered a boreal (sub Arctic), coldwater species.

Despite a range with a 30 degree latitude span (3,000 miles), all brook trout are thought to belong to the same species. Two subspecies, S. f. timagaminiensis (aurora trout) and S. f. agassizii (silver trout) have been described in the scientific literature. Aurora trout are found in Ontario, Canada; however, recent genetic analysis suggests that they are a color variant of Eastern brook trout and not a subspecies. Silver trout evolved in a large, extinct glacial lake in New Hampshire, and have been considered extinct from what are now Dublin Pond and Christine Lake since 1938.

While considered a single species, Eastern brook trout exhibit high genetic variation between populations. Brook trout in the Southern Appalachians differ genetically from northern populations, but a distinct latitude where “southern” diverges from “northern” is unclear as recent studies reveal that genetic composition of brook trout throughout their range is complex. With the many advances and retreats of glaciers that occurred over the past two million years, brook trout distributions fluctuated greatly and assembling a clear genetic history is difficult.

Trout Unlimited scientists working with many agencies and fish biologists developed a Conservation Success Index (CSI) that was used to create Figure 2. The various colors show where brook trout exist today in the U. S., and the status of specific populations. CSI ranges from stable strongholds (blue) to poor and very poor (orange and red, respectively), to extirpated (grey; locally extinct). Clearly, this map is cause for great concern as throughout their range in the eastern US, most populations are declining.

The thin line of brook trout populations in the Southeast shown in Figure 2 follow the spine of the Southern Appalachian Mountains with most populations occurring above 3,000 feet in elevation. Within these “sky islands” as higher mountains are referred to, brook trout exist in cool, clean streams in forested watersheds. Below 3,000 feet, habitat loss from human development (timber harvest, mining, agriculture, and urban development) and high summertime water temperatures (greater than 72 degrees F) severely restricts reproduction and survival of brook trout.

Unmanaged timber harvest and mining operations during the late 19th and early 20th centuries destroyed aquatic habitat and greatly impacted brook trout populations. Introduced rainbow trout (since 1885) and brown trout (since 1922) to replace collapsed brook trout fisheries quickly became established throughout the brook trout range. These populations of non-native trout were more tolerant than brook trout to declining habitat conditions and outcompeted brook trout in many streams. As forestry practices advanced during the 20th century and stream water quality and habitat improved, wild populations of rainbow and brown trout often suppressed the ability of brook trout to re-colonize their historic range.

In many streams; however, brook, rainbow, and brown trout exist together in a condition called sympatry. Why sympatry occurs in some streams and not others is not clear, but population genetics, specific habitat conditions, water chemistry, and biological productively likely integrate to reduce competitive exclusion. It is believed that sympatry is likely a tenuous and temporary condition, as variable environmental conditions will alternatively favor one species over another.

Most brook trout populations in the Southern Appalachian Mountains are isolated in high elevation streams. Prior to developmental and climate impacts of the past 150 years, brook trout populations were able to migrate throughout large drainage basins. This movement ensured high genetic diversity, recolonized populations that experienced random, catastrophic events (floods, fires, massive landslides, et cetera), and sustained brook trout through 2 million years of environmental change. Now, these isolated, fragmented populations cannot migrate within their drainages and exhibit low genetic diversity which reduces their capacity to adapt to variable conditions.

As the climate warms (Figure 3), some scientists predict that the southern extent of brook trout may shift northward. Figure 4 shows how warmer waters in the Gulf of Mexico and Atlantic Ocean are forcing the “average freezing line” northward. Since 1980, the U. S. Department of Agriculture’s planting zones have been adjusted in response to field measurements and climate modeling. Long term temperature data from Western North Carolina documents that the Southern Appalachian region is experiencing shorter, milder winters and warmer summers, particularly higher summer nighttime low temperatures which do not allow sufficient stream cooling overnight.  Precipitation patterns in the region are also changing as high winter rainfall events (3+ inches of rain/event) and summer droughts are both increasing in frequency and severity.

Some scientists contend that there is  potential for brook trout range regression northward within the next 50 to 100 years. The loss of brook trout in the Georgia, South Carolina, and Western North Carolina would be tragic. Southern Appalachian brook trout ( “speckled jewels”) are an iconic part of mountain cultural heritage, are highly-sought by anglers, and an important part of the ecosystem.

However, climate predictions are not absolute and brook trout show remarkable resilience and have persisted over many climatic changes over millions of years. What we do today has a tremendous impact on the eventual outcome for brook trout in the Southern Appalachians. Populations are disconnected, hanging on in the higher reaches of mountain streams. Threats include low genetic diversity, low population sizes, and more frequent flood events, especially winter events that can wipe out an entire year class of young fish. While brook trout tolerate acidic conditions better than other trout species, acid precipitation has been determined to be reducing brook trout populations in many streams in the Great Smoky Mountains National Park.

While the challenges that brook trout face are significant, there are reasons for conservation-minded citizens to be encouraged. Brook trout have existed over a wide range of environmental extremes and they possess the genetic potential to overcome many ecological hurtles. Efforts are underway to expand brook trout populations in the Southern Appalachians with diverse genetic compositions that help populations adapt. Introduction of brook trout into stream sections where fish are currently absent, and renovating rainbow and brown trout populations prior to stocking brook trout are being done in by the Great Smoky Mountains National Park and North Carolina Wildlife Resources Commission. These projects have shown success, and scientist’s ability to improve population abundance, genetic diversity, and resiliency are reasons for optimism.

Trout Unlimited’s Priority Waters Initiative (https://www.tu.org/magazine/priority-waters/priority-waters/) places a focus on rivers and streams that have the most conservation need for native species. Southern Appalachian brook trout populations are contained within this initiative. TU chapters from the southeastern states are working with the U.S. Forest Service, National Park Service, state fish and wildlife agencies, conservation organizations, and local communities to improve the outlook for brook trout that are hanging on in the edge of their range. Projects to protect watersheds, improve aquatic habitat, increase brook trout population size and genetic diversity, and reconnect isolated populations will add much needed resiliency, and hopefully allow brook trout to better adapt to a changing climatic conditions.

What is the Pisgah Chapter of Trout Unlimited doing to help ensure that brook trout will be enjoyed by future generations?

• Provide funding and volunteers for projects to improve habitat in the French Broad River watershed.
• Conduct surveys to document stream habitat changes, temperature monitoring, sediment sources, and barriers to fish passage in the Nantahala and Pisgah National Forests.
• Support projects at Great Smoky Mountains National Park with funding and volunteer manpower (fish population and water chemistry sampling).
• Collaborate with U. S. Forest Service and North Carolina Wildlife Resources Commission to develop management plans and projects to improve stream habitat and brook trout populations.
• Advocate for sound watershed management and stream buffer protection.
• Provide comments to Henderson County comprehensive plan.
• Inform and educate our youth, fellow citizens, elected officials, and business community on the great value brook trout provide to our economy, heritage, natural history, and quality of life.

The Pisgah Chapter of Trout Unlimited is asking our membership, supporters, and the other concerned citizens to help our efforts to conserve our precious Southern Appalachian brook trout. Please contribute financially and volunteer for our conservation and education projects and programs. To learn more, please go to www.pisgahtu.org.

Figure Citations/Sources:

Figure 1: Maine Department of Inland Fisheries and Wildlife. Augusta. ME. Accessed from https://www.maine.gov/ifw/docs/Biology_and_Management.pdf

Figure 2: Eastern Brook Trout Joint Venture. Accessed from https://easternbrooktrout.org

Figure 3: NOAA data published by Bateman, T. S. 2021. The Conversation. Phys.org online publication. Accessed from https://phys.org/news/2021-11-ways-proactive-climate-helpless-lessons.html

Figure 4: Rood, R. B. 2024. Living on the Edge. Michigan Today. University of Michigan. Ann Arbor, MI. Accessed from https://michigantoday.umich.edu/2024/01/26/living-on-the-edge/

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About the Author

Tom Champeau is a fisheries biologist who spent a 38-year career with the Florida Fish and Wildlife Conservation Commission, and was named a Certified Fisheries Scientist by the American Fisheries Society in 1985. He served as Chair of the National Fish Habitat Partnership for four years. Tom was elected to the Pisgah Chapter of Trout Unlimited Board of Directors in 2020. He is currently the PCTU’s Communications and Trout in the Classroom coordinator.