Survival Challenges for Brook Trout in Pennsylvania’s Warming Streams
As climate change continues to alter ecosystems globally, the native brook trout populations in southwestern Pennsylvania are feeling the heat. In the midst of the Laurel Highlands, on Laurel Hill, researchers have been studying the impact of rising stream temperatures on these cold-water fish, uncovering a worrying trend.
David Argent, a biology professor and fisheries scientist at PennWest University’s California, Pa., campus, along with his team, published a study in Environmental Management. They explored how varying stream temperatures in the Laurel Highlands affect brook trout (Salvelinus fontinalis). The findings revealed that despite the better performance of trout in groundwater-fed streams compared to surface water-fed streams, there is an overall decline in brook trout populations by 60 to 70 percent across the region.
David Argent explained: “Regardless of what type of stream we had, we saw a kind of widespread decline in populations of brook trout across the entire Laurel Hill, somewhere on the order of 60 to 70 percent.”
Understanding Thermal Sensitivity
The research aimed to uncover the thermal sensitivity of brook trout, which is the relationship between air temperature and stream temperature. Streams with dense overhead cover and groundwater sources were assumed to be less affected by climate change compared to those with open canopies and surface water sources. The study confirmed that groundwater-fed streams indeed harbored more stable brook trout populations.
Measuring Climate Change Impact
Researchers determined 18 degrees Celsius (mid-60s Fahrenheit) as the critical temperature for brook trout survival. The study tracked the number of days stream temperatures exceeded this threshold, indicating thermal stress on the fish.
In addition to temperature, other factors like water withdrawal, logging, and development projects contributed to the decline. Argent noted, “Climate change certainly didn’t help. But it was one of, we think, two or three other probably mitigating factors.”
Protective Measures for Brook Trout
To safeguard brook trout, Argent suggests protecting groundwater sources and maintaining riparian buffers, which are crucial for insulating streams and preventing sediment infiltration that disrupts trout reproduction. He also highlighted the threat of invasive species, like Japanese knotweed, to the riparian zones.
Argent emphasized: “[T]he best course of action would be to protect the water source, try to protect those groundwater sources as best we can. Maintain an intact riparian buffer.”
Unexpected Findings
Surprisingly, several streams now house fish that were not present at the study’s inception. While some streams received stocked fish, others contained what appeared to be wild fish, raising questions about their origins. Argent expressed concern over the unexpected 60% decline in brook trout, despite the remote and hard-to-reach nature of many streams.
The study underscores the complex interplay of climate change and human activities on aquatic ecosystems, highlighting the urgent need for conservation efforts to preserve these vital habitats.
Original Story at www.alleghenyfront.org