Projected population persistence of eastern hellbenders (Cryptobranchus alleganiensis alleganiensis) using a stage-structured life-history model and population viability analysis

Unger, Shem D.; Sutton, Trent M.; Williams, Rod N.

doi:10.1016/j.jnc.2013.06.002

Cited by 25 publications

(31 citation statements)

References 55 publications

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“…The next size class (9–12 cm) only made up 2% of captures. Assuming there was no net emigration of larval hellbenders within the study site over the first year, mortality rates of larvae post dispersal are ~ 90%, which is consistent with estimates for combined egg/larval survival provided by Unger et al [ 16 ]. Also, they used Lefkovitch stage structured matrices to show that a stable stage distribution should be characterized by a very high (~84%) egg/larva stage frequency.…”

Section: Discussionsupporting

confidence: 88%

“…This combination of longevity and iteroparity, secretive behavior, and the physical environment they occupy requires a very high investment in survey effort over many years to reliably estimate demographic parameters such as abundance, stage specific survival, recruitment and fecundity. These parameters are typically estimated through capture-mark-recapture (CMR) surveys, and are essential for constructing reliable stage structured matrix and population viability models [ 14 – 16 ], which can inform wildlife managers about population status, viability, and effective management strategies.…”

Section: Introductionmentioning

confidence: 99%

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Importance of demographic surveys and public lands for the conservation of eastern hellbenders Cryptobranchus alleganiensis alleganiensis in southeast USA

Freake

Perno

2017

PLoS ONE

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Comparisons of recent and historic population demographic studies of eastern hellbenders Cryptobranchus alleganiensis alleganiensis have identified significant population declines and extirpations associated with habitat degradation, poor water quality and disease, leading to nomination as a candidate for listing under the Endangered Species Act. However, populations in the southern Appalachian region of the range have received less attention despite relatively high levels of watershed protection due to the establishment of federally protected National Forest and National Park public lands. These watersheds likely represent some of the best remaining available habitat, yet the lack of published studies make assessment of population stability and viability very difficult. Our objectives were to (1) conduct a capture-mark-recapture (CMR) demographic study and a point transect survey on the Hiwassee River in Tennessee which is designated a National Scenic River, and is largely contained within the Cherokee National Forest, (2) quantify the size structure of the population, (3) compare abundance, survival and recruitment with historic and contemporary hellbender populations across the range, (4) assess the importance of this population and the significance of National Forest and National Park lands in the context of hellbender population conservation in the southeastern United States. We detected all age classes present, with larval hellbenders comprising 21.5% of captures. Using a combination of static life table and CMR methods, we determined that survival rates during the first year were low (~10%), but were high (68–94%) for taggable sized hellbenders. Density of hellbenders at the study site was very high (84 taggable sized hellbenders per 100m of river) compared to recent demographic studies conducted in other regions of the range. We detected hellbenders over ~28 km of river, with a mean density of 23 taggable sized hellbenders per 100m of river, and a total population estimate of 6440 taggable hellbenders. National Forest and National Park lands are likely to continue to play a particularly important role in providing suitable habitat for hellbenders in the southern Appalachians. In fact, only six of 21 known hellbender locations in Tennessee appear to show consistent larval recruitment, all of which are located within or adjacent to National Forest or National Park land.

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Section: Discussionsupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Importance of demographic surveys and public lands for the conservation of eastern hellbenders Cryptobranchus alleganiensis alleganiensis in southeast USA

Freake

Perno

2017

PLoS ONE

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“…Determining hellbender presence is important, but that alone might provide little information on population status. For instance, hellbenders are long-lived organisms (likely 30-50 years), and larger individuals may survive for many years even if no reproduction takes place (Unger et al, 2013). Thus, presence/absence of eDNA would not be able to distinguish functionally extinct populations represented by a single geriatric individual from reproducing populations.…”

Section: Introductionmentioning

confidence: 99%

Using environmental DNA methods to improve detectability in a hellbender (Cryptobranchus alleganiensis) monitoring program

Spear

Groves

Williams

et al. 2015

Biological Conservation

225

243

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“…Potential habitat differences among stage classes should be considered in future conservation and habitat restoration efforts, especially as accounting for multiple stage classes can assist in amphibian conservation efforts (Swanack et al, 2009). Immature individuals may be an important component for increasing some Hellbender population sizes as demonstrated by sensitivity analysis (Unger et al, 2013). Current Hellbender conservation efforts have focused heavily on head-starting and releasing individuals in order to boost adult populations.…”

Section: Discussionmentioning

confidence: 99%

Hellbender Salamanders (Cryptobranchus alleganiensis) Exhibit an Ontogenetic Shift in Microhabitat Use in a Blue Ridge Physiographic Region Stream

Hecht

Freake

Nickerson

et al. 2017

Preprint

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Organisms that experience large changes in body size during the life span often exhibit differences in resource use among life stages. Ontogenetic shifts in habitat use reduce intraspecific competition and predation and are common in lotic organisms. Although information on the immature life stages of the Hellbender (Cryptobranchus alleganiensis) is limited, this aquatic salamander exhibits ontogenetic shifts in habitat use in some streams, with adults sheltering under large rocks and larvae utilizing interstitial spaces of gravel beds. Due to the geomorphology of Little River, Tennessee, however, limited interstitial spaces within the gravel are filled with sand. Therefore, we quantified microhabitat parameters for three life stages of Hellbenders (larvae, sub-adult, adult) to determine if an ontogenetic shift in microhabitat occurred in Little River. We found no significant differences in stream substrate at capture sites among the stages, but there was a positive correlation between rock shelters underlain with very coarse gravel and overall Hellbender occupancy. Although we found no difference in water quality parameters and streambed particle size among the stage classes at the sites of capture, there was a significant difference in the average shelter size among all stages, with larvae utilizing the smallest shelters. Based on these results, future Hellbender research and conservation efforts should consider differences in life stage habitat use as well as specific stream particle classes.

show abstract

Projected population persistence of eastern hellbenders (Cryptobranchus alleganiensis alleganiensis) using a stage-structured life-history model and population viability analysis

Cited by 25 publications

References 55 publications

Importance of demographic surveys and public lands for the conservation of eastern hellbenders Cryptobranchus alleganiensis alleganiensis in southeast USA

Importance of demographic surveys and public lands for the conservation of eastern hellbenders Cryptobranchus alleganiensis alleganiensis in southeast USA

Using environmental DNA methods to improve detectability in a hellbender (Cryptobranchus alleganiensis) monitoring program

Hellbender Salamanders (Cryptobranchus alleganiensis) Exhibit an Ontogenetic Shift in Microhabitat Use in a Blue Ridge Physiographic Region Stream

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