Influence of Interacting Stressors on Native Brook Trout in a Western Pennsylvania Watershed

Elaine Langone Center, Terrace Room

Freshwater species have declined throughout their native ranges in part due to habitat fragmentation and invasive species. Information is often lacking, however, about how interactions between these stressors affect certain aspects of native populations. Brook trout (Salvelinus fontinalis) are a prime example of a species in decline due to human-related stressors, two of which are fragmentation from abandoned mine drainage (AMD) and competition with non-native brown trout (Salmo trutta). In an ongoing, multi-year study, we are assessing the abundance, behavior, and genetic structure of brook and brown trout in a western Pennsylvania watershed fragmented by AMD and scheduled for remediation in 2018. From past surveys, we predicted that AMD was acting as a chemical barrier to brown trout invasion into a tributary dominated by brook trout. This watershed represents a common situation in Pennsylvania—brook trout populations are simultaneously fragmented, yet “protected” from brown trout invasion by AMD, but remediation could permit brown trout invasion upstream. However, preliminary results show brown trout invasion has already begun prior to any remediation. We predict that as water quality improves after remediation, brown trout invasion upstream will accelerate, increasing interspecific competition with the resident brook trout. This trade-off between isolation and invasion presents a significant management challenge, and our study will highlight the need to be mindful of potentially negative outcomes stemming from AMD remediation efforts to the imperiled brook trout.