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1. Food availability leads to more connected contact networks among peridomestic zoonotic reservoir hosts

   https://doi.org/10.1098/rsos.230809  

   Kuenzi, Amy J. ; Luis, Angela D. ( November 2023 , Royal Society Open Science)

   The North American deermouse (Peromyscus maniculatus) is a reservoir host for many zoonotic pathogens. Deermice have been well studied, but few studies have attempted to understand social interactions within the species despite these interactions being key to understanding disease transmission. We performed an experiment to determine if supplemental food or nesting material affected social interactions of deermice and tested if interactions increased with increasing population density. We constructed three simulated buildings that received one of three treatments: food, nesting material, or control. Mice were tagged with passive integrated transponder (PIT) tags, and their movement in and out of buildings was monitored with PIT tag readers. PIT tag readings were used to create contact networks, assuming a contact if two deermice were in the same building at the same time. We found that buildings with food led to contact networks that were approximately 10 times more connected than buildings with nesting material or control buildings. We also saw a significant effect of population density on the average number of contacts per individual. These results suggest that food supplementation which is common in peridomestic settings, can significantly increase contacts between reservoir hosts, potentially leading to increased transmission of zoonotic viruses within the reservoir host and from reservoir hosts to humans.

    

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2. The impact of run-of-river dams on sediment longitudinal connectivity and downstream channel equilibrium

   https://doi.org/https://doi.org/10.1016/j.geomorph.2020.107568  

   Magilligan, F.J. ; Roberts, M.O. ; Mackenzie, M. ; Renshaw, C.E. ( January 2021 , Geomorphology)

   null (Ed.)

   Considerable research over the past several decades shows that dams, especially large, flow regulating structures, fragment watersheds and serve to disconnect the normative downstream flux of sediment and nutrients. Less attention has addressed smaller, channel-spanning Run-of-River (RoR) dams that are more commonly distributed throughout watersheds. Taking advantage of a suite of RoR dams in New England (USA), we quantify bedload flux into, through, and beyond the reservoir of five RoR dams and calculate the residence time of gravel clasts within the reservoir. To accomplish this goal, we embedded Radio Frequency Identification (RFID) PIT tags in 791 gravel clasts ranging in size from 15 mm to 81 mm which were subsequently deployed within and upstream of the impounded reservoirs. Among the 503 tracers that were transported from their deployment location, the median cumulative distance traveled was 30 m and the maximum cumulative displacement during the study period 758 m. Of the total tagged rocks placed at all five sites, 276 rocks were displaced over the dam, 204 of which spent time in the reservoir between high discharge events; the rest were transmitted downstream in a single high discharge event. Among those tracers that spent time in the reservoir prior to transmission over the dam, the average reservoir residence times at the different sites ranged from 19 - 203 days. The median grain size of tracers that were transported over the dam were identical to those that moved during the study period and similar to the median grain size of the channel bed. The distribution of virtual velocities of those tracers that moved was approximately log-normal and very broadly distributed over more than six orders of magnitude. An analysis of variance revealed that the distribution of velocities was partitioned into two statistically similar groups; with slower velocities in the two smaller watersheds (13 km2 – 21 km2) compared to the larger watersheds (89 km2 – 438 km2). We conclude that RoR dams transmit and trap the upstream sediment supply within the same range of physical conditions that produce mobility and trapping in the river’s natural reach-scale morphological units. Since RoR dams are likely not trapping more sediment than is typically sequestered in natural river reaches, these dams do not disconnect the normative downstream flux of sediment nor result in channel morphological disequilibrium downstream of the dam. However, the minimal effect that small, channel spanning RoR dams have on the morphological equilibrium state of a channel does not suggest that RoR dams have no ecological footprint. 

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3. Characterization of acoustic detection efficiency using a gliding robotic fish as a mobile receiver platform

   https://doi.org/10.1186/s40317-020-00219-7  

   Ennasr, Osama ; Holbrook, Christopher ; Hondorp, Darryl W. ; Krueger, Charles C. ; Coleman, Demetris ; Solanki, Pratap ; Thon, John ; Tan, Xiaobo ( December 2020 , Animal Biotelemetry)

   null (Ed.)

   Abstract Background Autonomous underwater vehicles (AUVs) and animal telemetry have become important tools for understanding the relationships between aquatic organisms and their environment, but more information is needed to guide the development and use of AUVs as effective animal tracking platforms. A forward-facing acoustic telemetry receiver (VR2Tx 69 kHz; VEMCO, Bedford, Nova Scotia) attached to a novel AUV (gliding robotic fish) was tested in a freshwater lake to (1) compare its detection efficiency (i.e., the probability of detecting an acoustic signal emitted by a tag) of acoustic tags (VEMCO model V8-4H 69 kHz) to stationary receivers and (2) determine if detection efficiency was related to distance between tag and receiver, direction of movement (toward or away from transmitter), depth, or pitch. Results Detection efficiency for mobile (robot-mounted) and stationary receivers were similar at ranges less than 300 m, on average across all tests, but detection efficiency for the mobile receiver decreased faster than for stationary receivers at distances greater than 300 m. Detection efficiency was higher when the robot was moving toward the transmitter than when moving away from the transmitter. Detection efficiency decreased with depth (surface to 4 m) when the robot was moving away from the transmitter, but depth had no significant effect on detection efficiency when the robot was moving toward the transmitter. Detection efficiency was higher when the robot was descending (pitched downward) than ascending (pitched upward) when moving toward the transmitter, but pitch had no significant effect when moving away from the transmitter. Conclusion Results suggested that much of the observed variation in detection efficiency is related to shielding of the acoustic signal by the robot body depending on the positions and orientation of the hydrophone relative to the transmitter. Results are expected to inform hardware, software, and operational changes to gliding robotic fish that will improve detection efficiency. Regardless, data on the size and shape of detection efficiency curves for gliding robotic fish will be useful for planning future missions and should be relevant to other AUVs for telemetry. With refinements, gliding robotic fish could be a useful platform for active tracking of acoustic tags in certain environments. 

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4. Life-Stage Differences in Microhabitat Use by Hellbenders (Cryptobranchus alleganiensis)

   https://doi.org/0018-0831-75.1.21  

   Jeronimo G. Da Silva Neto, William B. ( March 2019 , Herpetologica)

   Hellbenders (Cryptobranchus alleganiensis) are long-lived, fully aquatic salamanders that inhabit cool, well-oxygenated streams and rivers in the eastern United States. Although once abundant, C. alleganiensis populations have experienced major declines across the historical range. Habitat degradation, siltation, aquatic contaminants, and infectious diseases are commonly suggested as contributors to these declines. Although Tennessee provides areas of high-quality habitat for C. alleganiensis, microhabitat differences among life stages are not well documented. We evaluated microhabitat use of larval, subadult, and adult C. alleganiensis at three streams in east Tennessee by comparing sites occupied by C. alleganiensis to random sites within each stream. We used multivariate analysis to evaluate microhabitat use differences among larval, subadult, and adult C. alleganiensis. We completed habitat assessments for 60 individuals. We detected an association between C. alleganiensis presence (regardless of life stage) and the percentage of large rock, the percentage of low embedded rocks, and the number of rocks above 500 mm. Furthermore, the volume of cover rock, the number of rocks above 500 mm, the distance to bank, and the percentage of low embedded rocks, gravel, and sand were the most important microhabitat attributes to discriminate life-stage distributions. Overall, our analyses identify microhabitat attributes that are potentially important for long-term C. alleganiensis conservation and provide guidance for stream protection and restoration practices that might mitigate sedimentation and habitat degradation in impacted streams. 

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5. Weathering the storm: Improving the availability and stability of artificial shelters for hellbender salamanders

   https://doi.org/10.1002/rra.3722  

   Button, Sky T. ; Hallagan, John J. ; Bodinof Jachowski, Catherine M. ; Case, Brian F. ; Groffen, Jordy ; Hopkins, William A. ( September 2020 , River Research and Applications)

   Artificial shelters show considerable promise as tools for studying imperiled hellbender salamanders. Their full utility has not yet been fully reached in practice, however, because during initial trials shelters often became blocked by sediment or dislodged during high stream discharge events. To determine whether these challenges could be overcome, we deployed 438 artificial shelters of two different designs across 10 stream reaches and three rivers in the upper Tennessee River Drainage in 2013–2018. We recorded shelter entrance availability during surveys, and recorded which shelters became dislodged following high discharge events. We evaluated two hypotheses: (a) shelter availability was driven by shelter placement and maintenance frequency and (b) shelter stability was driven by shelter design and shelter placement. Shelters were available 78.6% of the time on average (range = 0–100%), and 88.6% (388 of 438) of shelters were stable across all high discharge events. Shelter availability was maximized by clearing sediment from shelter entrances at least once every 40 days (more often in impaired reaches with high siltation) and after large storm events, situating the shelter within 1 m of ≥5 boulders, and orienting shelters such that their entrances do not face directly downstream. Shelter stability with our initial shelter design was 77.5% (169 of 218), but approached 100% (219 of 220) for heavier (~40 kg vs. ~25 kg) shelters with recessed lids, and in reaches with abundant large boulders. Our findings demonstrate that with an improved design and careful placement, artificial shelters can serve as valuable tools for monitoring hellbenders in reaches with modest siltation.

    

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