Translocation does not influence amphibian chytrid fungus prevalence among translocated wild eastern hellbenders Cryptobranchus alleganiensis

Abstract

Disease monitoring is an essential step in translocation projects, specifically in amphibians where emerging pathogens such as the chytrid fungus Batrachochytrium dendrobatidis (Bd) are linked to population declines. The eastern hellbender Cryptobranchus alleganiensis is a large, fully aquatic salamander experiencing precipitous range-wide population declines; however, the role Bd plays in these declines is unclear. To augment declining hellbender populations and determine effects of translocation on Bd prevalence, we conducted a translocation study of wild adult hellbenders from 2 source streams with abundant hellbender populations to 2 streams with declining populations in east Tennessee, USA. In 2018, we implanted radio transmitters into 30 hellbenders and sampled them periodically for Bd until 17 of the 30 hellbenders were translocated in 2019. We attempted to recapture translocated hellbenders approximately every 45 d for 3 mo to determine Bd prevalence post-release. We used qPCR to detect Bd and quantify zoospore loads on positive samples. Hellbenders had a pre-translocation Bd prevalence of 50% (15 of 30), which decreased to 10% (1 of 10) post-translocation. The average zoospore load for positive samples was 73.63 ± 30.82, and no hellbenders showed signs of chytridiomycosis throughout the study. Although we detected no significant effect of translocation on Bd prevalence, we observed a reduction in Bd prevalence post-release. Our results indicate that translocation did not lead to an increase in pathogen prevalence in translocated wild adult hellbenders, suggesting that chytrid did not impact the success of short-term translocations of eastern hellbenders in the Blue Ridge ecoregion.

Evaluating translocation success of wild eastern hellbenders (Cryptobranchus alleganiensis alleganiensis) in Blue Ridge Ecoregion streams using pre- and post-translocation home range sizes and movement metrics

“…While large dam removal in many systems is unlikely to occur in the near future due to economic and environmental concerns [ 74 ], we found that translocation around dammed systems may provide an option to increase population connectivity of isolated freshwater species within a meaningful time frame. This strategy has been used successfully for a variety of other imperiled freshwater species, including mussels [ 75 ], fish [ 76 ], and now hellbenders [ 46 ]. However, release site selection is a critical piece of a successful freshwater translocation [ 19 ] and our study highlights the value of using pre-translocation monitoring to determine release site suitability and measure translocation success.…”

“…For individuals that were at least 150 g (n = 30), a 4 g model F1170 (pulse rate 15 ppm [708-day battery life]) radio-transmitter (Advanced Telemetry Systems, Isanti, MN) and a 12 mm passive integrated transponder (PIT) tag (Biomark, Boise, ID) were surgically implanted into the coelomic cavity on-site (performed by RHH, DVM, Ph.D.). Surgical protocols were carried out in accordance with Burgmeier et al [ 36 ], with a few adjustments (described further in [ 46 ]. All surgery and field protocols were approved by the Institutional Animal Care and Use Committee (IACUC) at Tennessee State University (Permit #1804WS).…”

“…We translocated 17 hellbenders from both source sites over five discrete events in the spring and summer of 2019. We translocated individuals in small groups to monitor dispersal tendencies of the released individuals over a settling period of ~30 days [ 46 ]. The number of individuals translocated in a given event was dependent on accessibility of animals at that time as well as their survival throughout the first year of the study.…”

“…After this initial intensive monitoring phase, individuals at both release sites were located every 3 ± 1 days throughout the summer and fall seasons until the first hard frost of the season (-2° C; 11 Nov 2019). We recaptured translocated hellbenders every 45 days (if accessible) to assess mass gains/losses as well as overall health [ 46 ]. During this same period, tracking continued at source sites for hellbenders that were not translocated (due to inaccessibility of animals under large rocks or ledges).…”

Encouraging news for in situ conservation: Translocation of salamander larvae has limited impacts on their skin microbiota

“…to Atlantic salmon fry (Uren Webster et al, 2020) and hellbender salamanders (Nolan, 2020). However, several translocation experiments report that the alpha diversity and community structure of microbiota are entirely determined by the environment of destination of translocated individuals (Bletz et al, 2016;Uren Webster et al, 2020).…”