Seasonal and diel signature of eastern hellbender environmental DNA

Examination of environmental DNA (eDNA) is a non-invasive conservation tool that has been used for the detection of aquatic organisms. When coupled with quantitative polymerase chain reaction (qPCR), eDNA sampling may be used to infer seasonal or diel activities of target species. To survey the status of eastern hellbenders (Cryptobranchus a. alleganiensis), fully aquatic cryptic salamanders of conservation concern, through eDNA analyses, we collected water samples monthly from 13 sites across 8 tributaries of the West Branch Susquehanna River in Pennsylvania, USA, from June through October 2014. We also examined the effects of the breeding season, diel activity, and stream environmental variables (e.g., temp, pH) on eDNA concentration estimates. We repeatedly detected hellbender eDNA from all 4 tributaries known to contain hellbenders, and from downstream sites of 2 of the 4 tributaries without known records of hellbenders. In the tributaries known to contain hellbenders, we observed notable increases in eDNA concentrations during the September breeding season, suggesting possible reproductive events. However, such seasonal eDNA signature was lacking from the eDNA positive sites of the tributaries without known records of hellbenders. There was no difference in eDNA estimates between diurnal and nocturnal samples, indicating that diel activity was inconsequential to eDNA estimates. Our statistical analyses of the eDNA positive sites revealed no effects of the stream variables on eDNA estimates. Yet, the presence of hellbenders was positively associated with stream temperature and negatively with pH. The positive association with temperature was likely to be an artifact of the sampling design, whereas the negative association with pH may indicate negative effects of farming and livestock on hellbenders. Our findings concur with recent studies on the importance of temporal sampling in interpreting eDNA signature in relation to life histories of target species. Further studies are needed to characterize the core habitats of newly found populations for future management of the declining hellbender populations. © 2017 The Wildlife Society.