Population Status of the Eastern Hellbender (Cryptobranchus alleganiensis alleganiensis) in Indiana

Studies that assess current and historical population densities accurately provide valuable information for management of wildlife species, particularly those in need of immediate conservation concern. The Eastern Hellbender (Cryptobranchus alleganiensis alleganiensis) has experienced drastic declines throughout its range during the previous few decades. This study documents its continued decline over the past 25 years in the last known remaining population in southern Indiana. We conducted mark recapture surveys from June 2008 to October 2008 and July 2009 to September 2009 at 35 sites. Despite a considerable increase in effort over previous surveys, we documented fewer total captures and extremely low population densities. Density was estimated at 0.06 individuals/100 m(2), and catch per unit effort was 0.05 individuals/person hour throughout the entire study area. This represents not only a significant decline in numbers from the historical study, but also is well below that reported for populations throughout the species' range. Sex ratios were skewed significantly toward males (2.6 males : 1 female). No subadults or larvae were found, and only two nests were located. This population consists almost exclusively of large, older-age class individuals that show limited signs of reproduction.