Last updated: October 8, 2024
Article
Brook Trout on the Brink
NPS Photo
“Brook trout are the canary in the coal mine,” said Dave Demarest.
Demarest is a wildlife and fisheries biological science technician at Shenandoah National Park in Virginia. He is a lifelong fisher and lover of the outdoors. “I started fishing at three years old. I tend to spend more time outdoors than in a building,” he said.
As the metaphor goes, canaries were once used to detect dangerous gases in coal mines. Just as canaries were early indicators of unsafe conditions, brook trout serve as indicators for environmental changes, more specifically in cold-water streams. As a fisheries biologist, Demarest spends much of his time measuring the stream temperatures. By the end of October, he will have installed temperature loggers at 47 fish monitoring sites throughout the park.
Unfortunately, warning signs are already flashing red at Shenandoah National Park and in other parks where brook trout are an iconic species that hold significant recreational, cultural, and ecological value.
NPS Photo
While no definitive evidence has been found in Eastern parks explaining the decline in brook trout populations, climate change may be a likely factor. Brook trout thrive in colder water, and higher elevation areas and locations with groundwater springs provide the cooler, stable temperatures they need. It is common for declining brook trout populations to be linked to agricultural impacts or a degrading landscape, but in a national park, those factors likely aren’t to blame. As air and water temperatures rise nationwide due to climate change, it is suspected that increasing stream temperatures are contributing to the decline in brook trout numbers.
In Shenandoah National Park, for example, two-thirds of the streams have seen brook trout numbers drop by an estimated 50 percent over the past 25 years. In some streams in Shenandoah, populations have vanished entirely.
“Our brook trout are pushing upstream from the lower elevation waters at the park boundary,” Demarest said. “We are the top of the watershed, and they are cold-water fish. They can only go so far upstream to find cold water.”
“Shenandoah has had a long-standing inventory and monitoring program for collecting data specifically focused on brook trout since the 1980s,” said Evan Childress, chief of natural and cultural resources at Shenandoah National Park. This provides baseline for the project.
While many park streams have shown a decline in brook trout populations, about 15 percent are showing increases. "Streams in areas with acid-sensitive geology, or those that were heavily impacted by acid rain, seem to be recovering to some extent now," said Childress.
However, the future remains uncertain for many streams. As water temperatures rise, some may no longer provide a suitable habitat for brook trout, but they may offer lessons parks can use to maintain high quality habitat in other streams, even in the face of climate change.
Inflation Reduction Act-Funded Study
As a first step to prevent further losses and with Inflation Reduction Act (IRA) funding, the National Park Service (NPS) is studying brook trout at Shenandoah and three other Eastern parks and developing a strategy that can be applied to parks across the eastern U.S.
Childress, who is coordinating the study in collaboration with U.S. Geological Survey scientists, learned of the brook trout’s plight as an aquatic ecologist at the park. The NPS will conduct it in three phases. First, parks and scientists will come together to determine priorities and approaches for cold-water resources under NPS stewardship across the eastern US. Second, they will assess the status of brook trout at Shenandoah National Park, Acadia National Park in Maine, Great Smoky Mountains National Park in Tennessee and North Carolina, and Catoctin National Park in Maryland. Finally, they will develop park-specific plans for how to proceed at the four parks to define specific actions that can be taken to meet NPS and park goals for conserving cold-water resources.
NPS / U.S. Geological Survey
To monitor brook trout, Shenandoah and the other three Eastern parks typically use electrofishing methods. This involves using a battery and probes to create an electric current in the stream, temporarily stunning the fish so they can be netted, counted, and then released unharmed. This systematic sampling allows researchers to estimate the total number of fish species in a particular area. In Shenandoah National Park, about 102 sites have been monitored periodically to assess brook trout numbers.
“Something we can do is prioritize protection of the forest to make sure that invasive species are not creating disturbances that jeopardize brook trout populations in streams where the future is relatively rosy,” said Childress. “So, we can identify and prioritize streams that
are going to be better suited for the species—even under the stress of climate change—and take actions to make sure they are protected from other kinds of disturbance.”
The Importance of Brook Trout
Brook trout are a key attraction for visitors seeking recreational opportunities. “Anglers love getting out there -- seeing and catching fish,” said Childress.
NPS / Anne Marie Pippin
Brook trout play a vital role in boosting tourism revenue, helping local businesses and communities that rely on visitors drawn to these natural wonders. In 2023 alone, 1.6 million park visitors spent an estimated $114 million in local regions while visiting Shenandoah National Park. This spending supported a total of 1,350 local jobs and $60.8 million in labor income in local economies surrounding the park.
This IRA-funded project will help Childress, Demarest, and colleagues find clues for the reason behind diminishing brook trout populations and eventually create a plan of action.