For our series, Reporting From the Mon, we’re diving into the Monongahela River and its tributaries. This time, we explore the Youghiogheny River in the Laurel Highlands. We’re focusing on how fish, specifically brook trout, are coping in our changing climate.
Kara Holsopple from The Allegheny Front interviewed David Argent, a biology professor and fisheries scientist at PennWest University. He just published a study in the journal Environmental Management examining the temperature shifts in streams around Laurel Hill and how these affect native brook trout (Salvelinus fontinalis). The findings reveal that while groundwater-fed streams support healthier trout populations, overall, there’s been a significant decline. They saw a drop of 60 to 70 percent in brook trout numbers.
Understanding Temperature’s Role
David explained their research began in 2012. Along with Dr. William Kimmel, they set up temperature sensors in selected streams and compared the current data to studies from the late 1980s. They wanted to see the changes over time, particularly concerning climate change.
David highlighted “thermal sensitivity,” the connection between air and stream temperatures. Streams shielded by dense canopies performed better than more exposed ones. Despite some streams performing better, they all faced a decline in brook trout populations.
MULTIFACTORIAL CHALLENGES
When asked about the causes behind the decline, David noted that temperature changes are just one part of the story—water withdrawal, logging, and urban development also play significant roles.
Interestingly, research shows brook trout are vulnerable to temperatures above 18 degrees Celsius (about 64 degrees Fahrenheit). If they remain exposed to those conditions for too many days, their survival rates drop.
Keeping Brook Trout Safe
To protect brook trout, David recommends preserving groundwater sources and maintaining healthy riparian buffers (the areas near streams). He stressed the importance of education and awareness regarding local development and logging activities that could harm these ecosystems.
He further pointed out that groundwater can be affected by human activities—like well drilling or water withdrawals for making snow at ski resorts.
The Ripple Effect of Invasive Species
Another concern David raised is the encroachment of Japanese knotweed in riparian areas, which can disrupt the ecosystem and negatively affect fish populations. This invasive species provides inadequate cover for stream insects, the key food source for brook trout.
Surprises in the Research
David was shocked by the steep decline in brook trout numbers, especially since many streams studied are remote and hard to access. Surprisingly, they also found brown trout in streams that historically didn’t have them—probably due to natural migration or hidden populations.
Conclusion
The ongoing challenges for brook trout highlight the need for a multifaceted approach to conservation. Addressing climate change, preserving groundwater, and controlling invasive species are essential steps to ensure the health of fish populations in our rivers.
For more insights on this topic, you can refer to the full study in Environmental Management.
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10 October 2025 episode
