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Objective: Visible implant elastomer (VIE) tags are commonly used as a cost‐effective tool for marking small fish, making them valuable in mark–recapture studies. It is crucial to quantify the impact of tagging procedures on fish survival to address inferential bias in mark–recapture studies. We assessed marking‐related mortality and growth in American Eel Anguilla rostrata elvers in a 40‐day laboratory experiment, following VIE tag application. Methods: There were 500 elvers (80–149 mm) that were divided into four treatment groups and one control group. Treatment groups were tagged with two tags in three body locations (anterior, central, posterior on left bilateral side) or with two tags in all three locations, while the control group remained untagged. Eels were retained in experimental tanks, and mortality rates were compared. Result: The VIE tagging did not significantly affect survival, which was 90.9% across all treatment groups and 92% for the untagged control group; nor did it affect growth. Conclusion: The application of VIE tags on various body parts should be a safe and effective method for marking American Eel elvers. Impact statementThe effect of visible implant elastomer tags on juvenile eel survival has only been assessed for European Eel, and tagging was restricted to tail fins. By testing novel tag locations on American Eel elvers, we demonstrated that this species can be tagged multiple times with visible implant elastomer tags without affecting short‐term survival and growth. [ABSTRACT FROM AUTHOR]

Migration rates, delay, timing, and success of acoustic-tagged Atlantic salmon (Salmo salar) presmolts (n = 120) and smolts (n = 57) are reported as they moved through the large Mactaquac Generating Station (MGS) reservoir and subsequently the lower Saint John River (SJR). The potential relationship between fish movements and the MGS operations was examined directly and via a hydrodynamic model. Migration rates were 15.4-29.3 km * [day.sup.-1] within the river sections and 5.0-13.3 km-day-1 through the reservoir, a significant reduction of 32%-57%. Migratory timing was temporally mismatched with dam operations such that only a few (n = 3) smolts had the option of dam passage via spill. Migration success estimated as apparent survival was high through the reservoir (81%-100%), declined by 8%-32% during passage at the MGS, and additional losses (27%-55%) occurred during the migration to the lower SJR, such that overall survival to the estuary for the groups tagged as autumn presmolts was 61%-65%, and survival for those tagged as spring smolts was 6%-10%. Le present article fait etat des vitesses, retards, moments et succes de la migration de saumons atlantiques (Salmo salar) dotes d'etiquettes acoustiques aux stades de pre-saumoneau (n = 120) et de saumoneau (n = 57), durant leurs deplacements a travers le grand reservoir de la centrale electrique de Mactaquac (CEM), puis dans le cours inferieur du fleuve Saint-Jean (FSJ). Le lien potentiel entre les deplacements des poissons et les activites a la CEM a ete examine directement et par l'entremise d'un modele hydrodynamique. Les vitesses de migration etaient de 15,4-29,3 km * [jour.sup.-1] dans les tronqons du fleuve et de 5,013,3 kmjour-1 dans le reservoir, pour une baisse significative de 32-57%. Le moment de la migration etait decale dans le temps par rapport aux activites au barrage, de sorte que seuls quelques saumoneaux (n = 3) avaient l'option de franchir le barrage par l'evacuateur. Le succes de migration, estime comme etant le taux de survie apparent, etait eleve dans tout le reservoir (81-100%) et diminuait de 8-32% durant le passage dans la CEM, d'autres pertes (27-55%) se produisant durant la migration dans le cours inferieur du FSJ, de sorte que les taux de survie globaux une fois l'estuaire atteint pour les groupes etiquetes comme etant des pre-saumoneaux de l'automne etaient de 61-65%, et pour ceux etiquetes comme des saumoneaux du printemps etaient de 6-10%., Introduction Migration of diadromous fishes is challenged worldwide by hydropower stations and the reservoirs they create, risking loss of some species such as eels (Anguilla spp.), shads (Alosa spp.), and [...]

Physical habitat models represent a widely used tool in river management, yet, there is a growing consensus—particularly for large rivers—that fundamental principles have limits, and it is evident that improved methodologies for assessment and design are needed. Here, we suggest a framework that takes steps towards resolving some of these issues, using changes of fish habitat in a large, regulated river as a case study. First, we propose using hydrodynamic modelling in combination with a fuzzy rule-based classification as a tool to delineate and quantify meso-scale fish habitat. Variability in spatial and temporal extent of mesohabitats can be modelled across a range of flows and under non-wadable conditions when standard mesohabitat surveys become largely unfeasible. Second, research effort and empirical data on habitat use and preference of fishes is typically focused on a small group of species and limited for many imperilled or elusive taxa; we suggest using expert knowledge to expand beyond one or a few species to build the biological models for a community-level assessment until empirical data becomes available. Third, sources of uncertainty that are linked to both fundamental elements of habitat models, namely the biological and hydrodynamic components, need to be quantified and reported in modelling outcomes. The steps described in our modelling framework represent key tools for river managers charged with developing environmental flows guidelines in large, regulated rivers. [ABSTRACT FROM AUTHOR]

Reservoir formation in a river system changes a lotic environment to more lacustrine conditions, with impacts throughout the ecosystem. In this study, a river reach containing typical salmonid riffle/run habitat was flooded to create a large, deep pool from June to September in each of 3 years. We test the hypothesis that juvenile Atlantic salmon (Salmo salar) with their preference for run/riffle habitats will respond to the transformation to a lentic environment by moving into adjacent lotic environments. Movements of juvenile Atlantic salmon were monitored using a combination of biotelemetry (radio‐ and passive integrated transponder‐tagging) and electrofishing. Results showed that no tracked fish moved away from the created pool habitat. Mass‐specific growth rates showed the created pool habitat resulted in net growth of juveniles. The results confirm that fish may not immediately (i.e., at least for an approximate 2 months) respond to rapid, large‐scale habitat alterations by moving to find similar habitat conditions outside the altered habitat. This is most probably related to plasticity of behavior and habitat use, and no change in biological conditions to a point that would negatively impact fish growth and survival, for example food availability, competition, or predation. The results also support the hypothesis that the relative importance of physical habitat variables is not universal among streams and populations, therefore limiting the value of applying standard habitat suitability criteria and use. [ABSTRACT FROM AUTHOR]

Potential for shale gas production is linked to regional geology, which influences water chemistry of freshwater systems. However, there has been little work to establish baseline ecological conditions of rivers within areas of shale gas development. In this study, water chemistry and monitoring metrics for fish and benthic macroinvertebrates were compared among varying-sized streams in New Brunswick, Canada, with different underlying geology. Water chemistry and biotic community structure differed strongly among geological age classes. Early Carboniferous stations, with highest potential for shale gas production, had the highest ions, invertebrate abundances, and richness of invertebrates and fish, with strongest differences between Early Carboniferous and Older Classes of bedrock. A reference condition model indicated numerous sites deviated from normal, but this was not specific to geological classes and reflected the lack of model reference site coverage. These results highlight the importance of selecting appropriate reference sites for bioassessment in areas of resource development to ensure that response to perturbation is differentiated from natural variability along environmental gradients in geology and resource-dependent variables that potentially influence aquatic ecosystem composition. Le potentiel de production de gaz de schiste est relie a la geologie regionale qui, elle, influence la chimie de l'eau dans les systemes d'eau douce. Peu de travaux ont toutefois tente de determiner les conditions ecologiques de base des rivieres dans des regions de mise en valeur du gaz de schiste. Dans la presente etude, la chimie de l'eau et des parametres utilises pour la surveillance des poissons et macroinvertebres benthiques sont compares entre cours d'eau de differentes tailles sous- tendus par differentes formations geologiques, au Nouveau-Brunswick (Canada). La chimie de l'eau et la structure des communautes biotiques varient fortement entre les classes d'age geologique. Les stations reposant sur des formations d'age carbonifere precoce, qui presentent le plus grand potentiel de production de gaz de schiste, montrent les plus fortes concentrations d'ions, abondances d'invertebrees et richesses d'invertebres et de poissons, les differences les plus grandes etant entre les formations d'age carbonifere precoce et les classes de substrat rocheux plus anciennes. Un modele des conditions de reference indique que de nombreux sites s'ecartent de la normale, mais cela n'est pas propre aux classes geologiques et reflete la couverture insuffisante de sites de reference pour le modele. Les resultats soulignent l'importance de choisir des sites de reference convenables pour les evaluations biologiques dans des regions de mise en valeur des ressources, afin de bien distinguer les reactions aux perturbations de la variabilite naturelle le long de gradients environnementaux de la geologie et de variables dependant des ressources qui pourraient influencer la composition des ecosystemes aquatiques. [Traduit par la Redaction], Introduction Monitoring and metrics of water quality and biotic community structure are necessary tools for meaningful assessment of potential impacts on freshwater ecosystems (Bonada et al. 2006; Arciszewski et al. [...]

Objective: Passive integrated transponder (PIT) telemetry is commonly used to monitor fish movements and behavior. To reduce inferential bias in PIT telemetry studies, it is important to quantify the effects of tagging procedures on fish survival. To this end, we conducted a controlled experiment to test the hypothesis that intraperitoneal injection of 23‐mm PIT tags would have no effect on the survival of adult Blueback Herring Alosa aestivalis. Methods: We compared mortality rates of tagged and untagged Blueback Herring (n = 174; size range 202–277 cm) that were retained in experimental tanks for 14 days. Result: We observed no difference in the probability of survival between tagged (50% survival) and untagged (42%) groups. Conclusion: These results suggest that intraperitoneal tag injection is a safe and effective method of PIT tagging adult Blueback Herring and supports the use of this technique in field telemetry studies. Impact statementWhile PIT telemetry is frequently used to monitor fish movements and behavior, few studies have evaluated the effect of tagging procedures on fish survival. By comparing the survival of control and treatment groups retained in experimental tanks for 14 days, this study found that intraperitoneal injection of 23‐mm PIT tags had a negligible effect on the survival of Blueback Herring. [ABSTRACT FROM AUTHOR]

Fragmentation of stream networks from anthropogenic structures such as road culverts can affect the health of a catchment by negatively affecting the ecosystem's biota, their movements, abundance, and species richness. We present a framework using publicly available LiDAR and orthophotography to locate and identify road crossings, i.e. the most prolific of barriers in forested landscapes, and evaluate fragmentation and passability at the landscape scale. Coupling the LiDAR stream network and private road network in the 3,223 km2 study area, we identified 1,052 stream crossings of which, 32% were culverts and 12% of the total stream network was potentially inaccessible due to these culverts. We correctly identified the type of stream-road crossings at >90% of any stream order and at 100% at Orders >2. The 10 culverts restricting the most stream kilometers, restricted >34% of the potential stream habitats for four species of fish, a result that provides the resource management with a first assessment for effective improvement of connectivity across this landscape. With this framework, managers equipped with appropriate imagery can create a stream crossing database with minimal funding, create an inventory of instream barriers, and prioritize removals at a landscape-scale, thus providing an effective assessment and decision-making tool for their habitat restoration efforts. [ABSTRACT FROM AUTHOR]

Thermal refuges are becoming increasingly influential for dictating the population status and spatial distribution of cold-water stenotherm salmonids in the mid- to southern extent of their range. The global climate is predicted to continue to warm, and therefore, the overall thermal suitability of freshwater habitats for stream salmonids is predicted to decline in concert. However, stream and river thermal heterogeneity will offer considerable resiliency for these populations. Thermal refuges are formed by many physical processes; common natural refuges include cold tributary plumes, groundwater springs, alcoves, and hyporheic upwellings. However, many anthropogenically formed refuges (such as stratified reservoirs or cold-water tailrace outflows) also exist in hydropower-regulated rivers. The significance of these refuges to stream salmonids depends on their size and temperature differential, but also other habitat characteristics such as their depth, flow velocity, Froude number, and many biotic factors within the refuges. Modern technologies such as drone-mounted thermal infrared cameras and other remote sensing techniques allow for the efficient identification of such refuges, and inexpensive options include the identification of refuges during ice cover using orthophotographs. Behavioural thermoregulation, i.e., salmonids aggregating in cold-water refuges, can be either facultative or obligate and the timing of these events is governed by life stage, species, and population-specific physiologically regulated cumulative thresholds that are inherently related to the recent thermal history, or hysteresis, of each individual. Salmonids appear to have an excellent spatial cognition for locating and relocating cold-water refuges, and their spatial distribution is largely affected by the availability of the cold-water refuges during the warm-water period in many thermally stressed rivers. Gregarious behaviour is the norm for salmonid fishes within the thermal refuges; however, the size/microhabitat hierarchy appears to dictate the within-refuge distribution at the micro-scale. There continues to be a great impetus for protecting—and in carefully determined cases creating—cold-water refuges in the future. A thorough understanding of what a "goldilocks" refuge is for various salmonids and their different life stages will be imperative as cold-water restoration is gaining popularity. Finally, disentangling the roles of the climate-induced and landscape activity-induced warming potential of fluvial freshwater will be important to ensure continued environmentally responsible landscape activities in future waterscapes. [ABSTRACT FROM AUTHOR]