Wanner, Cameron, Clean Water Institute, Lycoming College, 1 College Place, Williamsport, PA 17701, wancame@lycoming.edu; Kaunert, Matthew, Clean Water Institute, Lycoming College, 1 College Place, Williamsport, PA 17701, kaunert@lycoming.edu; Rieck, Leslie O., Clean Water Institute, Lycoming College, 1 College Place, Williamsport PA 17701, rieck@lycoming.edu.
The Eastern Hellbender (Cryptobranchus a. alleganiensis) represents an ancient lineage of giant (≤ 2.5 ft.), long-lived (> 25 years) stream-obligate salamanders. Land use change has resulted in range-wide population declines in the past 50 years. However, stream systems in northwestern Pennsylvania contain high quality hellbender habitat and are thus considered to be one of the last remaining strongholds for the species. Beginning in 2025, PennDOT has scheduled multiple bridge replacement projects in an Allegheny River tributary that harbors a high biodiversity of sensitive stream taxa, including regionally significant hellbender populations. Such construction activity may result in elevated sediment loads and impaired water quality as well as direct mortality within local hellbender populations. In summer 2024, we conducted multiple mark-recapture surveys to provide baseline data regarding hellbender demography and habitat quality at three stream reaches within the proposed bridge replacement project area. We used traditional rock-lifting survey techniques (2 surveys per reach) to assess hellbender population size/structure and shelter rock habitat quality. We estimated population size at each reach using an intercept-only POPAN model using program RMark in program R and provide descriptive statistics for population density, sex ratio, and age/size class structure. We recorded 107 capture events (n = 84 unique individuals) across six survey occasions. Population density ranged from 0.17 – 0.95 hellbenders per 100m2 habitat and sex ratios were relatively balanced across all three reaches. Old adults made up the majority of populations at sites A (0.71) and B (0.68), compared to site C, which was comprised mainly of young adults (0.42) and sub-adults (0.17). Shelter rock availability was relatively high across study sites (0.61 – 0.83), and shelter occupancy ranged from 0.07 – 0.15. Post-construction surveys will be conducted to evaluate bridge replacement effects on hellbender demography and habitat use/availability. We will deploy continuous water quality probes to evaluate changes in water quality and sedimentation rates. Artificial nest boxes may be installed to augment habitat loss resulting from construction activity. These data will also be integrated with long-term (10+ years) datasets for future population modeling and estimation of population persistence within the watershed.
amphibian decline, land use, construction, hellbender