Characterizing Stream Reaches Occupied by Eastern Hellbender (Cryptobranchus alleganiensis alleganiensis): Insights from A Previously Undocumented Western North Carolina Stream Population

Abstract

Abstract The Eastern Hellbender (Cryptobranchus alleganiensis alleganiensis) is a large aquatic salamander found in cool, highly oxygenated rivers and streams of the eastern United States. Hellbender populations have been steeply declining over the past century, and they are a protected species in many states, including North Carolina where they are listed as a species of special concern. North Carolina contains over 2,000 waterways that could potentially support hellbender populations. It is vital to survey these waterways to better understand the distribution of the Eastern Hellbender and the environmental factors necessary to support populations. Although small streams could potentially act as refugia for both larval and adult hellbenders, most surveys have focused on large rivers, generally using substrate composition and cover rock presence as site selection determinants. In early summer of 2013, we surveyed Bent Creek, a small (25.3 km2) catchment in the Pisgah National Forest beginning at the confluence with the French Broad River and concluding upstream to the Lake Powhatan dam. We documented four adult Eastern Hellbenders, including two captures and two tactile encounters/escapes. These represent the first records for C. a. alleganiensis in this catchment. In October 2013, we compared the number of cover rocks, water temperature, dissolved oxygen and substrate composition of three occupied and three unoccupied stream reaches. Although temperature and dissolved oxygen did not vary among reaches, occupied stream reaches had coarser substrates and a much higher occurrence of cover rocks than unoccupied reaches. Our findings suggest that commonly used surveying techniques relying on potential cover rocks and substrate composition are effective methods for selecting survey sites. Future research could examine whether the Eastern Hellbender population at Bent Creek is, or has the potential to become, a viable breeding population, as well as assessing population size upstream from Lake Powhatan. Suitability of stream conditions to consistent larval recruitment should also be evaluated. Our findings suggest that smaller streams such as Bent Creek can support viable populations of C. a. alleganiensis, and that restricting surveys to larger watersheds has the potential to miss important populations of this imperiled species.