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Diadromous fish populations have incurred precipitous declines across the globe. Among many stressors, these species are threatened by anthropogenic barriers that impede movement, alter riverine habitat, and augment predator communities. In this study, we used acoustic transmitters (n = 220) with predation and temperature sensors to characterize Atlantic salmon (Salmo salar) smolt predation risk in the Penobscot River, Maine, USA. Across two seasons, we documented 79 predation events through a 170 km migratory pathway, which included three hydropower projects and a large estuary. We detected tagged smolts that were predated by fish (n = 42), marine mammals (n = 28), and birds (n = 9). Using a multistate mark- recapture framework, we estimated that 46% of smolts were predated during downstream migration, which accounted for at least 55% of all mortality. Relative predation risk was greatest through impoundments and the lower estuary, where on average, predation rates were 4.8-fold and 9.0-fold greater than free-flowing reaches, respectively. These results suggest that predation pressure on Atlantic salmon smolts is exacerbated by hydropower projects and that predation in the lower estuary may be greater than expected. Key words: predation, salmon, dams, telemetry, migration, Introduction Human-mediated changes to river systems (e.g., climate change, habitat degradation, and introduction of non-native species) may alter predator-prey dynamics (Alexander et al. 2015; Thakur et al. 2017; Murphy et [...]

Management boundaries are often delimited by political and social factors, whereas animal movements are affected by ecological and geophysical constraints. Thus, understanding connectivity among distinct management units is of considerable importance, particularly for harvested species, where quotas set in ignorance of connectivity may fail to meet management goals.We constructed an individual‐based model (IBM) to better understand wild turkey movements at large scales, benefiting from multiple data sources that are often available for harvested species.We built an IBM from spring seasonal movements of wild turkey, using data from ringed, radio‐, and GPS‐marked turkeys captured in Maine, USA. Our IBM accommodated variation in individual turkey response to landscape connectivity metrics and identified emergent migratory connectivity dynamics among harvest management regions.We calculated a low degree of connectivity among wildlife management districts (WMD) which, in combination with the substantial number of boundary crossings observed, indicated a more diffuse distribution of turkeys among WMDs.Synthesis and applications: Estimates of turkeys moving between districts provided a clear delineation of where immigration was strongest, identifying which WMDs should be managed as singular population units. This approach has widespread utility for any species or system where harvest management decisions are made at finer spatial scales than the movement dynamics affecting population processes. [ABSTRACT FROM AUTHOR]

American eel (Anguilla rostrata) often pass hydropower dams during adult spawning migrations. We conducted a 4-year acoustic telemetry study that characterized passage risks through two dams (West Enfield and Milford) in the Penobscot River, Maine, USA. We released tagged fish (n = 355) at two sites, estimated survival and delay under variable river conditions, and compared performance among dammed and free-flowing river sections. Survival rates (standardized per river kilometre, rkm) were lower at West Enfield ([[PHI].sub.rkm] = 0.984 [+ or -] 0.006 SE) and Milford ([[PHI].sub.rkm] = 0.966 [+ or -] 0.007 SE) compared with undammed River sections ([[PHI].sub.rkm] = 0.998 [+ or -] 0.0003 SE). Cumulative mortality was 8.7% (4.4 km) and 14.2% (5.5 km) through dammed sections and 8.7% throughout the rest of the river (58.1 km). Fish that already passed an upstream dam incurred higher downstream mortality compared with individuals without passage experience. Additionally, fish endured long delays at dams, and >10% of fish were delayed >24 h. Low flows exacerbated the risk of mortality and delay. These results offer evidence for direct, latent, and sublethal consequences of dam passage for migrating eels. Des anguilles d'Amerique (Anguilla rostrata) adultes passent souvent a travers de barrages hydroelectriques durant leurs migrations de frai. Nous avons mene une etude de telemetrie acoustique de quatre ans qui a permis de caracteriser les risques associes au passage a travers deux barrages hydroelectriques (West Enfield et Milford) sur le fleuve Penobscot (Maine, Etats-Unis). Nous avons relache des poissons etiquetes (n = 355) en deux sites, estime la survie et le retard dans des conditions variables du fleuve et compare les performances entre des troncons du fleuve endigues et a ecoulement libre. Les taux de survie (normalises par kilometre de cours d'eau, rkm) etaient plus faibles a West Enfield ([[PHI].sub.rkm] = 0,984 [+ or -] 0,006 Et) et Milford ([[PHI].sub.rkm] = 0,966 [+ or -] 0,007 Et) que dans les troncons non endigues du fleuve ([[PHI].sub.rkm] = 0,998 [+ or -] 0,0003 ET). La mortalite cumulative etait de 8,7 % (4,4 km) et 14,2 % (5,5 km) dans les troncons endigues et de 8,7 % dans tout le reste du fleuve (58,1 km). Les anguilles qui etaient deja passees par un barrage en amont presentaient une mortalite plus forte en aval que les specimens sans experience de passage. En outre, les poissons subissaient de longs retards aux barrages, ce retard etant de >24 h pour >10 % des anguilles. De faibles debits exacerbaient le risque de mortalite et la duree des retards. Ces resultats temoignent de consequences directes, latentes et subletales du passage de barrages pour les anguilles en migration. [Traduit par la Redaction], Introduction Diadromous fish species have experienced substantial population declines over the last 200 years, with many Atlantic stocks currently $40 million (USD) in 2012 (ASMFC 2017). Low recruitment has led [...]

The bridle shiner (Notropis bifrenatus) is a small cyprinid native to the eastern United States and Canada. Bridle shiner populations have declined across their range, and the species now receives concern status or legal protection in 13 states and two provinces. Bridle shiners were historically found in southern and western Maine in densely vegetated, shallow habitats along the shorelines of streams and ponds. We surveyed areas of Maine that supported historical bridle shiner populations using environmental DNA (eDNA) and traditional seine netting methods, and then used eDNA sampling to survey areas with unknown bridle shiner presence. We rediscovered bridle shiner populations at 11 of 32 historically occupied waterbodies and documented bridle shiners in four additional waterbodies. We determined that both eDNA and seine net surveys are viable options for monitoring bridle shiners in Maine and identified ways to streamline the eDNA methods used in this study to reduce the time and cost of future surveys. [ABSTRACT FROM AUTHOR]

Context. Stress or injury resulting from capture and marking of animals is a potential cause of mortality following release. Multiple methods have been developed to identify sources of postcapture mortality, but these are most often applied following completion of field work to identify an appropriate censor window for other analyses. Aims. Following unacceptable levels of post-capture mortality (13 of 53) in radio-marked individuals in the first year of a larger wild turkey research project in Maine, USA, we assessed post-capture survival as data became available to inform proactive changes to capture protocols, with the goals of improving animal welfare and data quality. Methods. We evaluated potential sources of post-capture mortality related to the capture and marking process, individual characteristics of the turkey, and local weather conditions. We then used results from the preliminary analysis to inform adaptive changes to capture protocols in subsequent years and confirmed the effectiveness of these changes through a final analysis. Key results. We found that greater handling time was positively correlated with increased postcapture survival, possibly in response to releasing turkeys in larger groupsto facilitate regrouping. We also found that transmitter style impacted post-capture survival, such that female turkeys fitted with backpack-style transmitters experienced a survivalrate of 0.787 (0.677–0.861 95%CI), compared with 0.903 (0.538–0.976 95% CI) for those fitted with a necklace transmitter, although adjustments to the fit of backpack transmitters appeared to help mitigate such issues. Conclusions. Following informed adjustments to our capture protocols, we observed a dramatic increase in post-capture survival such that no mortalities were experienced in the first 30 days post capture in the final year of our study (n= 65).Although our estimated censor window wassimilarto otherstudies(~10 days), differencesin effects of external stressors further the need for adaptive capture protocols because local stressors and risks may vary according to climate and ecosystem characteristics such as predator communities and habitat type. Implications.We recommend that when possible, investigators continuously assess their protocols throughout the capture process and adapt accordingly to limit negative repercussions of capture and handling to wildlife. [ABSTRACT FROM AUTHOR]

For wide‐ranging species in temperate environments, populations at high‐latitude range limits are subject to more extreme conditions, colder temperatures, and greater snow accumulation compared with their core range. As climate change progresses, these bounding pressures may become more moderate on average, while extreme weather occurs more frequently. Individuals can mitigate temporarily extreme conditions by changing daily activity budgets and exhibiting plasticity in resource selection, both of which facilitate existence at and expansion of high‐latitude range boundaries. However, relatively little work has explored how animals moderate movement and vary resource selection with changing weather, and a general framework for such investigations is lacking. We applied hidden Markov models and step selection functions to GPS data from wintering wild turkeys (Meleagris gallopavo) near their northern range limit to identify how weather influenced transition among discrete movement states, as well as state‐specific resource selection. We found that turkeys were more likely to spend time in a stationary state as wind chill temperatures decreased and snow depth increased. Both stationary and roosting turkeys selected conifer forests and avoided land covers associated with foraging, such as agriculture and residential areas, while shifting their strength of selection for these features during poor weather. In contrast, mobile turkeys showed relatively weak resource selection, with less response in selection coefficients during poor weather. Our findings illustrate that behavioral plasticity in response to weather was context dependent, but movement behaviors most associated with poor weather were also those in which resource selection was most plastic. Given our results, the potential for wild turkey range expansion will partly be determined by the availability of habitat that allows them to withstand periodic inclement weather. Combining hidden Markov models with step selection functions is broadly applicable for evaluating plasticity in animal behavior and dynamic resource selection in response to changing weather. We studied turkeys at northern range limits, but this approach is applicable for any system expected to experience significant changes in the coming decade, and may be particularly relevant to populations existing at range peripheries. [ABSTRACT FROM AUTHOR]