Duke, Hannah, Clean Water Institute, Lycoming College, 1 College Place, Williamsport, PA 17701, dukhann@lycoming.edu; Rieck, Leslie O., Department of Biology, Lycoming College, 1 College Place, Williamsport, PA 17701, rieck@lycoming.edu; Andrew, Dave, Department of Biology, Lycoming College, 1 College Place, Williamsport PA 17701, andrew@lycoming.edu.
The American Eel (Anguilla rostrata) is an important species of freshwater fish native to North America. As critical hosts of the glochidia of several threatened and/or endangered freshwater mussel species, American Eel population health and persistence is of increasing interest in the Susquehanna River basin. Barriers along streams (dams, culverts, etc.) can impede eel migration, preventing natural spawning behavior, though additional impacts on population persistence are unknown, though likely of interest to conservation efforts. The Susquehanna River Basin Commission (SRBC) has stocked approximately 60,000 eels in the Pine Creek Watershed in north-central PA since 2010. There is a paucity of information on where those eels have moved and whether they have traversed barriers in the area to spread throughout the drainage system. eDNA saves time in detecting elusive species, minimizes damage to individuals (vs. electrofishing), and may be more accurate than electroshocking, particularly when used for species that frequently burrow. A species-specific marker to test for eel DNA in qPCR analysis was developed a few years ago with very high accuracy. Here, we used this method at five sites in Pine Creek and its tributaries in Tioga County, PA to assess the current distribution of American Eel near where stocking activities had previously occurred. Two sites were immediately at SRBC stocking locations, while three were upstream or downstream of the stocking locations, separated by barriers inventoried in the North Atlantic Aquatic Connectivity Collaborative (NAACC)’s stream barrier database. Most of these barriers had been surveyed and evaluations had determined that they were not likely to be a hindrance to aquatic organism passage, while some barriers remain unsurveyed. We used a Smith-Root eDNA backpack and previously developed qPCR procedures, along with the recently developed American Eel qPCR markers, to extract and quantify the American Eel eDNA in our samples. In short, we filtered 1 L of stream water using a 0.45 μm self-preserving filter, extracted DNA from filters using the DNEasy Blood and Tissue Kit, then used 15 μL qPCR reactions using a CFX Opus 96 Real-Time PCR System. We designed a gBlock to use as a positive control and for developing a standard curve to quantify eel DNA in field samples. Following successful in-lab sampling to ensure the protocol worked, we sampled five field sites adjacent to stocking locations in the Pine Creek valley. We found eel eDNA at only one site downstream of the stocking site on the main branch of Pine Creek. In the future, electrofishing or other surveying should take place to confirm continued eel presence in the area. Incorporating more data from the NAACC database and surveying the unsurveyed crossings may be relevant in understanding how stocked eels move throughout a drainage basic. Expanding sampling sites to include areas of active eel stocking by SRBC may also help identify major influences on eel movement and success, including water quality, prey abundance, and other potential predictors. Eventually, these data could help develop models to predict where eels might be most successfully stocked in the future.
eDNA, American Eel, Barriers