Passive Integrated Transponder Tags Research Articles

Reappraising the use of forearm rings for bat species

Long-term mark-recapture studies are essential for bat conservation. Over the last decades, millions of bats across Europe and America have been marked with forearm rings for this purpose. Although it is considered a cost-effective method compared to Passive Integrated Transponders (PIT) tags, direct injuries from using forearm rings have been reported since their very first use. Yet, their impact on bats' welfare has not been systematically evaluated and remains a highly controversial issue among the scientific community and policymakers. Here we assess the impact of forearm rings and PIT tags on the health of different bat species. We reviewed 12 years of the existing recapture data of free-ranging bats from NE Spain and evaluated the impact of both marking tools in a captive colony of Carollia perspicillata, by assessing the development of skin lesions and levels of cortisol metabolites in guano (CG) after marking. We report that 55.1 % (435/790) of the recaptured free-ranging bats with forearm rings presented skin lesions. All banded C. perspicillata (n = 22, 100 %) developed skin lesions, whereas none of the PIT-tagged (n = 21) presented lesions. Levels of CG were significantly higher after marking with forearm rings only for one group. Banded C. perspicillata exhibited discomfort-associated behaviours due to forearm rings. Under the “precautionary principle”, we recommend the ban of forearm rings for all bat species until species-specific studies under controlled conditions are performed and approved by a legally constituted ethics committee. Consideration of other long-term marking tools is mandatory to align with global bat conservation strategies.

Stray compositions of hatchery‐origin Chinook Salmon and steelhead in natural spawning populations of the upper Columbia watershed

AbstractObjectiveOne of the biggest concerns of operating hatchery salmonid programs is high straying of returning adults into nontarget populations and the possible homogenization of genetic diversity among populations caused by spawning of stray fish. The composition of hatchery‐origin stray Chinook Salmon Oncorhynchus tshawytscha and steelhead O. mykiss relative to the natural spawning populations, termed “recipient population stray composition,” was evaluated at three spatial scales in the upper Columbia River basin, where stray target limits were 5–10%.MethodsChinook Salmon carcasses were collected from 1999 to 2018 in spawning areas shortly after spawning, and carcasses were examined to determine origin. Steelhead strays and spawning escapement were evaluated using passive integrated transponder tags between 2013 and 2018. We calculated mean stray compositions for 1999–2018 and for 2014–2018.ResultThe mean recipient population stray compositions ranged between 0.02% and 87.35% and increased with decreasing spatial scale. Recipient stray compositions of all taxa at the basin scale were <3%, and summer and fall Chinook Salmon were <0.5%. Stray compositions in subbasins for all taxa ranged between 0.07% and 33.04%. Spring and summer Chinook Salmon exceeded 5% and 10% (summer Chinook Salmon) in some periods in the Entiat and Methow River subbasins, but stray compositions for all Chinook Salmon were <5% in the Wenatchee, Okanogan, and Hanford Reach subbasins for all periods. All steelhead stray compositions in subbasins exceeded 5%, except for those in the Wenatchee subbasin. Stray compositions of spring Chinook Salmon in tributaries ranged between 0.61% and 87.35%. Only the Chiwawa, Icicle, and Twisp rivers were consistently below 10%.ConclusionIn cases where recipient stray management targets were exceeded, some were the result of single hatchery contributions but others were the result of cumulative contributions from multiple hatcheries. Some solutions to reduce recipient stray compositions will likely involve a combination of changes to hatchery, harvest, and habitat management.

Testing the effects of passive integrated transponder (PIT) tags on survival, growth, and tag retention of common nase (Chondrostoma nasus L.) and European barbel (Barbus barbus L.)

Freshwater fish populations are in steep decline, prompting conservation measures and a need for their evaluation. Fish are increasingly monitored with passive integrated transponders (PIT), although the suitability of this tagging technique has not yet been validated for most European target species of conservation. Consequently, this study tested the effect of commonly used 12 mm full-duplex (FDX) PIT tags implanted into the abdominal cavity of common nase (Chondrostoma nasus L.) and European barbel (Barbus barbus L.). A controlled laboratory setup was used to compare survival, growth (both length and weight) and tag retention for two different size classes of sub-adults over 61 days. Survival in the treatment groups was high (96.7–100%) and not statistically different from the control groups (97.5–100%). Highest mortality occurred in small tagged barbel (n = 4; 96.7% survival), while no mortality occurred in large tagged nase. Mean growth rates for tagged fish (2.28 mm, 3.26 g) were similar to those of control fish (2.77 mm, 3.59 g). Overall tag retention rate was 99.0% and tag loss only occurred in nase. The results of this study demonstrate the suitability of PIT injection in the body cavity of nase and barbel > 100 mm TL, which is of high methodological importance given the increasing role these species play in PIT tag-based assessments of freshwater fish conservation in European rivers.

Development and use of a large, flexible antenna to detect fish implanted with passive integrated transponder tags

Development and use of a large, flexible antenna to detect fish implanted with passive integrated transponder tags

Influence of channel geomorphic units on bedload transport and river morphology during low‐magnitude bed‐forming floods coupled with sediment augmentation

AbstractIn this study, we map different types of channel geomorphic units in a sediment‐starved, residual‐flow reach before and after an artificial flood. Bedload particles of a previous sediment augmentation measure are tracked with passive integrated transponder tags, and water depth and flow velocity are recorded across 10 cross‐sections. The analysis focuses on the influence of channel geomorphic units on bedload transport and river morphology. Our hypotheses are (i) that during low‐magnitude bed‐forming floods with sediment pulse migration, existing channel geomorphic units influence bedload transport, and more specifically, (ii) that their type influences the retention rate of bedload particles. Furthermore, we hypothesise that (iii) the density of channel geomorphic units is linked to the hydromorphological diversity of a river section. We provide evidence that supports the first two hypotheses and contradicts the third one. We consider our results to be transferable to similarly regulated reaches based on an analysis of site‐specific conditions and alternative explanatory factors. Further research is needed to transfer the results to varying flood and sediment supply conditions in unregulated reaches.

Distribution and straying of minijack Chinook Salmon released from a captive broodstock hatchery program

AbstractObjectiveProduction of Chinook Salmon Oncorhynchus tshawytscha in hatcheries can unintentionally produce large numbers of age‐1 males, termed "minijacks," which pose ecological and genetic risks to target and nontarget populations. We evaluated the postrelease distribution of minijacks produced in a hatchery captive broodstock program targeting the White River in the Columbia River basin between 2010 and 2015.MethodsFish were passive integrated transponder (PIT)‐tagged in the hatchery (n = 218,555), and databases were searched to determine movement behavior and final detections on fixed PIT tag antenna arrays during the year in which they were released.ResultTwo main movement behaviors were detected: (1) residuals, which moved solely within the subbasin of release; and (2) migrants, which moved downstream into the Columbia River and then reascended the Columbia River in the year of release. Minijacks that reascended fish ladders in the Columbia River were most often detected at Rock Island and Bonneville dams, the nearest and furthest detection locations downstream of the Wenatchee River. Minijacks were last detected in all locations where spring Chinook Salmon spawn in the Wenatchee River subbasin (seven tributaries and one main‐stem area) and also in the Entiat River (an adjacent watershed); minijacks in eight of the nine locations were considered strays. Estimates of minijacks that strayed outside of the White River were between 61% and 100% annually and were influenced by release location. Minijacks were also more abundant than males of all older ages in some of the tributaries during some years. In addition, they were detected in these tributaries during periods when anadromous adults migrate into spawning areas and when spring Chinook Salmon spawn.ConclusionThe large amount of minijack production and the spatial and temporal overlap could pose genetic and ecological risks to both target and nontarget populations and particularly high straying poses risks to the maintenance of between‐population genetic variability.

Passage Efficiency of Alewife in a Denil Fishway Using Passive Integrated Transponder Tags

AbstractPopulations of river herring (Alewife Alosa Pseudoharengus and Blueback Herring A. aestivalis, collectively), once abundant in coastal rivers along the Atlantic coast, have seen precipitous population declines, likely due to many factors, including commercial fishing, habitat degradation, and dam construction. Efforts to restore populations include the construction of fishways at dams, but upstream passage success of fish through fishways is variable. To evaluate passage efficiency of a fishway on the Lamprey River in Newmarket, New Hampshire, Alewives were PIT tagged in 2013 (n = 621) and 2014 (n = 501) and antennas monitored fish in 2013–2015. Potential handling effects, diel movement patterns, and fishway saturation negatively affected passage success. The probability of Alewives successfully passing through the fishway into the river above the dam increased with total length. The estimated probability of passage success of an Alewife of mean total length (280 mm and 292 mm for males and females, respectively) that migrated back to the dam at least 1 year after tagging was 0.63 for males and 0.64 for females. Fishway selectivity presents a potential bias in data collection in freshwater systems, and our results suggest that sampling below a fishway should be coupled with data collected from within and above the fishway for a more complete demographic sample of the migratory population.

Investigating patterns and extent of predation of hatchery-reared juvenile Nechako white sturgeon (Acipenser transmontanus) by North American river otter (Lontra canadensis) in the Nechako River, British Columbia, Canada

Predation of fish released as part of conservation aquaculture programs may undermine conservation goals. Identification of factors influencing predation, therefore, can inform management decisions that minimize predation losses. For the endangered Nechako white sturgeon ( Acipenser transmontanus Richardson, 1836), the survival of individuals released as part of a conservation aquaculture program is threatened by river otter ( Lontra canadensis (Schreber, 1777)) predation. Through the recovery of sturgeon passive integrated transponder (PIT) tags from otter latrines, we set out to quantify the extent of predation, identify spatial patterns in predation including identifying predation hotspots, and understand the timing of predation. The recovery of 3.9% of PIT tags from the hatchery-released sturgeon represents a minimum predation estimate based on several identified factors. The distribution of predation hotspots varied by release cohort, with some consistent hotspots among cohorts. An apparent decrease in predation in recent years was seen in conjunction with fewer live captures and lower release numbers, suggesting some level of density-dependent predation. Results from this study can be used to contribute to management decisions related to Nechako white sturgeon recovery efforts, inform further research needs, and contribute to a growing knowledge of sturgeon predation.

Flexible‐Pass‐Through Antennas for Half‐Duplex Passive Integrated Transponder Tags in Medium to Large Rivers Used to Study Size‐Selective Reservoir Passage

AbstractThe use of passive integrated transponder (PIT) tags for studying fish behavior and demography in medium‐large rivers is hindered by antenna designs that are susceptible to damage in those environments and low detection efficiencies. We designed a vertically oriented, flexible PIT tag antenna for half‐duplex tags that is simple to construct and deploy, resilient to the dynamic river environment, retains the higher detection efficiency of pass‐through antennas, and is suitable for rivers up to 30 m wide and 1.5 m deep. These “flexible‐pass‐through antennas” are economical to build and cost ~US$435 to $680 for a one‐ or two‐winding antenna, respectively. We used two flexible‐pass‐through antennas to test for size‐selective reservoir passage in juvenile steelhead Oncorhynchus mykiss (anadromous Rainbow Trout) and Rainbow Trout. We found that flexible‐pass‐through antennas withstood high flows and debris during a spring out‐migration season and provided data to reject the hypothesis of size‐selective fish passage at the Los Padres Dam and Reservoir on the Carmel River (California, USA).

Autumn outmigrants in brown trout (Salmo trutta) are not a demographic dead-end.

Genetic identity analysis and PIT (Passive Integrated Transponder) tagging were used to examine the freshwater return rates and phenotypic characteristics of n=1791 downstream migrating juvenile Salmo trutta in the Burrishoole catchment (northwest Ireland) across the period September 2017 to December 2020. In this system, juveniles out-migrate (move from freshwater into brackish or marine habitats) in every month of the year, with distinct seasonal peaks in spring (March through June; mostly silvered smolts) and autumn (September through December; mostly younger, unsilvered fry or parr). Both types exhibited a sex-bias towards females, which was stronger in spring (78% females) than in autumn outmigrants (67%). Sixty-nine returning fish were matched back to previous juvenile outmigrants and similar return rates were found for spring outmigrants (5.0%), autumn outmigrants (3.3%) and fish that outmigrated outside of spring or autumn (2.8%). Spring and autumn outmigrants returned at similar dates (typically mid to late July) but autumn fish were away for longer (median=612 days; spring outmigrants=104 days). Autumn outmigrants were 25% smaller than spring outmigrants at outmigration and 6% smaller on their return, and within both groups smaller/younger outmigrants spent longer away than larger/older outmigrants. Autumn outmigrants were more likely to return unsilvered as 'slob' trout (84%) than spring outmigrants (31%), suggesting they make greater use of brackish habitats that might be safer, but less productive, than fully marine habitats. However, both types also produced silvered 'sea trout' (≥1+ sea-age), implying neither is locked into a single life-history strategy. Our findings emphasise that autumn outmigrants and the transitional habitats that support their persistence should not be overlooked in salmonid management and conservation. This article is protected by copyright. All rights reserved.

Diverse environmental cues drive the size of reproductive aggregation in a rheophilic fish

BackgroundAnimal migrations are periodic and relatively predictable events, and their precise timing is essential to the reproductive success. Despite large scientific effort in monitoring animal reproductive phenology, identification of complex environmental cues that determine the timing of reproductive migrations and temporal changes in the size of reproductive aggregations in relation to environmental variables is relatively rare in the current scientific literature.MethodsWe tagged and tracked 1702 individuals of asp (Leuciscus aspius), a large minnow species, and monitored with a resolution of one hour the size of their reproductive aggregations (counts of sexes present at the breeding grounds standardized by the sum of individuals in the season) over seven breeding seasons using passive integrated transponder tag systems. We examined the size of reproductive aggregations in relation to environmental cues of day number within a reproductive season (intra-year seasonality), water temperature, discharge, hour in a day (intra-day pattern), temperature difference between water and air, precipitation, atmospheric pressure, wind speed and lunar phase. A generalized additive model integrating evidence from seven breeding seasons and providing typical dynamics of reproductive aggregations was constructed.ResultsWe demonstrated that all environmental cues considered contributed to the changes in the size of reproductive aggregations during breeding season, and that some effects varied during breeding season. Our model explained approximately 50% of the variability in the data and the effects were sex-dependent (models of the same structure were fitted to each sex separately, so that we effectively stratified on sex). The size of reproductive aggregations increased unimodally in response to day in season, correlated positively with water temperature and wind speed, was highest before and after the full moon, and highest at night (interacting with day in a season). Males responded negatively and females positively to increase in atmospheric pressure.ConclusionThe data demonstrate complex utilization of available environmental cues to time reproductive aggregations in freshwater fish and their interactions during the reproductive season. The study highlights the need to acquire diverse data sets consisting of many environmental cues to achieve high accuracy of interpretation of reproductive timing.Graphical abstract

Survival and swimming performance of a small-sized Cypriniformes (<em>Telestes muticellus</em>) tagged with passive integrated transponders

Italian riffle dace (Telestes muticellus, Bonaparte 1837) is a small-bodied Leuciscidae native to the Italian Peninsula, of which little is known about the ecology and individual movements in nature. Passive Integrated Transponder (PIT) telemetry is used to track fish movements and behaviour. The basic assumption is that the PIT-tagged organism's performances do not differ considerably from their natural behaviour. Here we present the first evaluation of potential tagging effects in the genus Telestes. The survival rate and tag retention were compared between two different tag implantation methods – injector gun and scalpel incision - and pit-tagging effects on swimming performance were evaluated. Five weeks after tagging, Italian riffle dace demonstrated high survival rates in all treatments: 94.8% for fish tagged with injector gun (n=58), 100% for scalpel incision method (n=58), and 98.3% for controls (n=58). The tag retention was 96.6% for gun treatment and 100% for scalpel treatment. Prolonged swimming performance, tested 22-23 days after tagging, showed a reduction in endurance (time-to-fatigue) for scalpel treatment (n=22) compared to the control group (n=21), while no difference in maximum swimming velocity was observed. We conclude that PIT tagging is a suitable technique for Italian riffle dace, showing high survival and PIT retention and no effect on maximum swimming speed. Significantly lower prolonged swimming performance, although likely less ecologically important, shows that tagging is not without costs. Potential biases need to be evaluated on a study-by-study basis, and future studies should explore behavioural tagging effects in nature.

Retention of passive integrated transponder tags in hatchery brook trout: Effect of tag size, implantation site, and double tagging

AbstractA fundamental assumption of mark‐recapture studies is that individuals do not lose their marks or tags, because tag loss can lead to biased parameter estimates. Retention of 8‐mm full‐duplex and 12‐mm half‐duplex passive integrated transponder (PIT) tags implanted in the abdomen, opercular musculature, and dorsal sinus of age‐0+ hatchery male brook trout (Salvelinus fontinalis) was evaluated in the laboratory. Treatments included single‐ and double‐tagged fish. Survival, growth, and tag retention were monitored for 181–187 days for 640 tagged fish and 80 untagged controls. Survival to 180 days ranged 95%–100% and was not affected by tagging. PIT‐tagging caused a short‐term reduction in growth rates. Tag retention to 180 days was 100% for dorsal implantation, 83.0% with 8‐mm tags in the operculum, 97.5% with 8‐mm tags in the abdomen, and 99.6% with 12‐mm tags in the abdomen. Retention of opercular tags was positively related to size at tagging. Tag loss was independent of whether fish were single‐ or double‐tagged. Double tagging with one full‐ and one half‐duplex PIT tag in different body locations would hedge against data loss relative to single tagging, especially for longer‐lived and iteroparous species where tag loss through time is more likely.

Survival rates of band‐tailed pigeons estimated using passive integrated transponder tags

AbstractObtaining survival estimates on the Interior population of band‐tailed pigeons (Patagioenas fasciata) is challenging because they are trap shy, but the joint use of passive integrated transponder (PIT) tags and bands is a potential solution. We investigated the use of PIT tags to passively recapture band‐tailed pigeon at 3 locations in New Mexico, USA, to estimate survival. From 2013–2015, we captured, banded, and marked >600 individual band‐tailed pigeons with PIT tags. To estimate annual survival rates, we used a Barker multi‐state joint live and dead encounters and resighting model. Survival models excluding transience had survival estimates across site, sex, and year of 0.86 (95% CI = 0.84–0.88) for after hatch year birds and 0.63 (95% CI = 0.48–0.76) for hatch year birds. These results are consistent with other survival estimates reported for the Interior population of band‐tailed pigeons using band return data and potentially provide an effective alternative method of monitoring survival of this population.

A perched culvert and natural obstructions limit fish dispersal in an intermittent prairie stream

Poorly constructed road crossings block upstream movement of fish into stream reaches that provide critical habitat or connect isolated populations. Although removing these barriers is often a conservation priority, quantifying fish passage following removal has not been well studied, particularly in intermittent streams. In this study, we sought to understand how barriers influence the dispersal of fishes in intermittent prairie streams. We used passive integrated transponder tags and antenna stations to quantify fish movement of 3 prairie-stream fishes (Central Stoneroller Campostoma anomalum [Rafinesque, 1820], Southern Redbelly Dace Chrosomus erythrogaster [Rafinesque, 1820], and Creek Chub Semotilis atromaculatus [Mitchill, 1818]) through a road crossing in an intermittent prairie stream for 3 y before and 3 y after removing a perched culvert. We verified that no upstream fish movement occurred through the culvert, despite large aggregations of tagged fish in the intermittent reach below the culvert. In contrast, tagged individuals of all 3 species were detected above the road crossing in each of the 3 y following removal. We also tracked the recovery of these species, plus the Orangethroat Darter Etheostoma spectabile (Agassiz, 1854), following a severe drought in 2018 in 2 spring-fed tributary reaches, 1 without a downstream barrier and 1 with the removed downstream culvert. Surveys of the tributary reaches showed rapid recovery of fish densities following drought in the tributary without a downstream barrier. However, recovery at the site above the removed culvert appeared to be limited by a natural waterfall. Our observations suggest barrier removal allowed access to spawning habitat within the intermittent reach immediately upstream of the site, but other obstacles or shear distance to perennial spring-fed tributary reaches also limited recolonization following severe drought. Increased connectivity between perennial and intermittent reaches in prairie streams likely benefits fishes by increasing their resilience following disturbance and providing habitat during critical life stages.

A Small Warm Tributary Provides Prespawning Resources for Colorado Pikeminnow in a Cold Dam-Regulated River

Abstract Riverine habitat mosaics, including tributaries, are an important reason the Green River subbasin supports the largest remaining population of federally endangered Colorado Pikeminnow Ptychocheilus lucius in the Colorado River Basin. Upstream Colorado Pikeminnow distribution is limited by Flaming Gorge Dam and few typically occurred in the reach immediately downstream of the dam, which is the reach most affected by thermal and hydrologic alterations. However, fish captures and passive integrated transponder (PIT) antenna sampling of previously tagged individuals from 2011 to 2021 revealed seasonal congregations of up to 75 Colorado Pikeminnow annually in the mouth of Vermillion Creek, a small tributary in the regulated reach. Approximately 11% (N = 93 individuals) of the entire 2017–2018 Green River basin population were encountered in Vermillion Creek over the 11-y study, an underestimate of use considering that untagged fish were not detected by antennas. Colorado Pikeminnow used Vermillion Creek primarily when Green River spring flows from Flaming Gorge Dam were high and cold in May through mid-June when the confluence was a large, deep backwater warmer than the main channel and supported forage fishes. Intra-annual encounters revealed seasonal residence times for individual Colorado Pikeminnow up to 91 d, and multiple inter-annual encounters indicated site fidelity. Frequent detections of individual Colorado Pikeminnow in a Yampa River spawning area soon after their detections in Vermillion Creek indicate this tributary may be an important resource for reproductive adults. The intensive and basin-wide PIT tagging and detection program for Colorado Pikeminnow enhanced our understanding of the importance of small habitat nodes such as Vermillion Creek in the Green River drainage network. Understanding and protecting these seasonally available riverine habitat mosaics used for prespawning conditioning may assist with recovery of Colorado Pikeminnow.

Active movement to coarse grained sediments by globally endangered freshwater pearl mussels (Margaritifera margaritifera)

The freshwater pearl mussel Margaritifera margaritifera is an endangered bivalve which is usually regarded as sedentary, although individual movement has been observed both vertically and horizontally. Little is known about the causes and rates of mussel movement. The objective of this study was to test the effect of microhabitat characteristics on the horizontal movement distance and rates of freshwater pearl mussels. A total of 120 mussels (length range 40–59 mm) were marked individually with passive integrated transponder tags, placed in stream microhabitats differing in their sediment composition and monitored biweekly over a period of 10 weeks. Mussels situated in sand-dominated habitats had a significantly higher mean movement rate (3.2 ± 4.2 cm/day, mean ± SD) than mussels situated in gravel-dominated (1.9 ± 2.7 cm/day) or stone-dominated habitats (1.8 ± 3.2 cm/day). The direction of the movements appeared random; however, an emigration from sandy habitats was observed, probably to avoid dislodgment from these hydraulically unstable habitats. This study demonstrates that freshwater pearl mussels can actively emigrate from unsuitable microhabitats. Once suitable streams with respect to physical, chemical, and biological quality were identified, it is therefore only necessary to identify suitable mesohabitats (area of 10–30 m2) when reintroducing or relocating mussels.

Post‐emergence movements and habitat use by hatchling diamondback terrapins

AbstractDiamondback terrapins (Malaclemys terrapin) inhabit estuarine environments, and adult females typically nest in coastal uplands. Hatchlings emerging from nests overwinter on land and in coastal salt marshes, but the proportions that use each land cover type is not well documented. From 2019 to 2021, we tracked movements and habitat use of hatchlings post‐emergence to determine the importance of upland overwintering sites to a terrapin population in Rhode Island, USA. In late summer and early fall, we attached a radio‐transmitter and passive integrated transponder (PIT) tag (n = 46) or only a PIT tag (n = 132) to carapaces of hatchlings emerging from nests. From August to June, we tracked the hatchlings via radio‐telemetry and a sweeping PIT tag antenna, successfully documenting the fates of 46.6% of them (n = 83). This group included 23 hatchlings that overwintered in the upland, 11 hatchlings that moved to the salt marsh in fall, 46 predated hatchlings, and 3 hatchlings dead from unknown causes. Upon emergence from their nests, 68% of hatchlings dispersed toward water and 32% of hatchlings dispersed away from water. In the uplands, hatchlings typically overwintered within about 2 m of habitat edges. Movement in the uplands peaked from late August to early October, then ceased until hatchlings re‐emerged in late April through early June. To protect terrapins, we recommend limiting the use of heavy equipment (e.g., mowers, tillers) in vegetated uplands near nest sites, and scheduling vegetation management for colder months (Nov–Mar in New England, USA) when hatchlings are inactive.

Climate‐driven stream‐flow impacts on bull trout metapopulation dynamics revealed by quantitative assessment of 22 years of tag–recapture data

Abstract Climate change has altered annual hydrologic cycles globally. Where stream flows are dominated by snow melt in western North America, climate change has resulted in peak flows that occur earlier in the runoff season and reduced flows during the non‐runoff season. Such changes can negatively affect the reproduction success and first‐year survival of stream‐dependent, autumn‐spawning salmonid fishes. We annually sampled bull trout (Salvelinus confluentus Suckley) populations in the St. Mary River catchment in north‐central Montana, U.S.A. Bull trout (≥ age 3; n = 3,502) electrofished from six creeks during 1998–2018 were given passive integrated transponder tags and 739 (21.1%) of those fish were recaptured through 2019 (tag loss c. 4.5%). We used tag–recapture data to (1) determine the spatial extent of the bull trout metapopulation; (2) fit a Bayesian Jolly–Seber model to identify the temporal trends in the sizes, finite growth rates (λ), and apparent survival and detection probabilities of the three main populations; and (3) assess the statistical associations between λ and flow. Bull trout movements among creeks defined the metapopulation's almost catchment‐wide spatial extent. Statistical correlations between λ and flow were clumped in the month × flow variable space at flow lags of 3–7 years, which corresponded with production of the dominant age classes in our tagged populations. Positive correlations occurred during June–September (the bull trout spawning season) and negative correlations during October–May (the embryo‐incubation period). Declining spawning‐season flow could have degraded bull trout spawning habitat, whereas increasing incubation‐period flow could have physically disturbed embryos affecting their survival. This study revealed associations between bull trout population dynamics and climate change as indexed by stream flow. Although the spawning habitats of these bull trout are protected within Glacier National Park and the occurrence of multiple local populations supports metapopulation persistence, that persistence is diminished because flow‐regime change has a strong negative influence on each population. Given the region's apparent climate trajectory, further decline in the bull trout metapopulation is anticipated.

Roost fidelity partially explains maternity roosting association patterns in Myotis lucifugus

Resources that draw individuals to a specific location may result in the formation of groups and development of individual social preferences. Simultaneously considering both ecological and social factors can therefore reveal underlying mechanisms of group formation and organization. Females of some temperate bat species roost in groups during the spring and summer months within which they give birth to and nurse their pups. Females switch roosts frequently, but the factors that influence roost switching remain poorly understood. To characterize the structure of a bat maternity group and gather evidence for the role of social preference in shaping this structure, we used roost co-occurrence data from little brown myotis, Myotis lucifugus , implanted with passive integrated transponder tags and roost boxes monitored with passive readers in Salmonier Nature Park, Newfoundland, Canada. By developing informed null models, we more directly investigate hypotheses that may explain why bats roost together. Although our results suggest that association patterns of maternity groups can largely be explained by similar interindividual patterns in bats' roosting frequencies within a given roost box (roost fidelity), other factors are likely to contribute to the observed structure. We thus provide support for the potential influence of roost and social preferences in shaping maternity group structure. • Female bats frequently switch roosts, changing who they roost with each day. • Some bats did not roost together at frequencies expected by chance. • Other bats occasionally roosted together more than expected by chance. • Social preferences may be important in influencing roosting decisions.