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System-wide survival of hatchery-reared Atlantic salmon (Salmo salar) smolts was evaluated (2017-2019) in the Penobscot River and compared to survival estimates from previous years that spanned major changes (2005-2016). This system was transformed through two dam removals in 2012 and construction of a nature-like passage structure at a third. The main stem had three dams (five prior to 2012), while the main tributary had four dams (one with the new nature-like passage). We estimated survival using acoustic telemetry mark-recapture (n = 1482) from 2017 to 2019. Six release sites and two release dates were included to assess system-wide survival. Survival from 2017 to 2019 was higher than previous years, with total cumulative survival > 0.75, independently of year and release sites, compared to survival < 0.5 in previous years. These years coincided with exceptional high flows not seen previously. We found an effect of delays on survival, longer delays associated with lower survival. Overall, survival in these years increased in all reaches relative to previous years except for one dam, Weldon Dam, which was a site of sustained high mortality. Key words: survival, dams, migration, salmon, fish movement La survie a l'echelle du reseau de smolts de saumon atlantique (Salmo salar) eleves en ecloserie a ete evaluee (2017- 2019) dans le fleuve Penobscot et comparee a des estimations de la survie pour des annees anterieures marquees par des changements majeurs (2005-2016). Ce systeme a ete transforme par le retrait de deux barrages en 2012 et la construction d'une passe d'aspect naturel a un troisieme barrage. Le cours principal comptait trois barrages (cinq avant 2012), alors que l'affluent principal en comptait quatre (dont un dote de la nouvelle passe d'aspect naturel). Nous avons estime la survie sur la base d'etiquettes de telemetrie acoustique recuperees (n = 1482) de 2017 a 2019. Six lieux de lacher et deux dates de lacher ont ete inclus pour evaluer la survie a l'echelle du reseau. La survie de 2017 a 2019 etait plus elevee que durant les annees precedentes, soit une survie cumulative totale de >0,75, independamment de l'annee et du lieu du lacher, comparativement a une survie de Mots-cles : survie, barrages, migration, saumon, deplacement du poisson, Introduction The downstream migration of Atlantic salmon (Salmo salar) juveniles is a critical stage in their life cycle. During this stage, individuals undergo a series of morphological, physiological, and behavioral [...]

Little attention has been given to optimizing statistical power for monitoring stream fish assemblages. We explored the relationship between temporal variability and statistical power using 34 metrics from fish community data collected annually at six sites over 10 years via electrofishing. Metric variability differed by the life stage and group of species considered, use of abundance or mass data, and data standardization technique. Lower variability was associated with community data, abundance data, and time-based standardizations, while greater variability was associated with young-of-the-year data, mass data, and area-based standardizations. Simulation-based power analysis indicated metric choice, and to a lesser degree, monitoring design (annual, biennial, endpoints, or haphazard sampling) influenced power to detect change. Across a fixed number of surveys (N = 60), endpoints sampling performed best. The N needed to detect change was heavily dependent upon metric choice for all monitoring designs, with the most biologically specific metrics requiring greater N. Large savings in effort and resource expenditure can be obtained utilizing biologically relevant metrics that are robust to temporal noise within an appropriate sampling design. L'optimisation de l'efficacite statistique pour la surveillance des assemblages de poissons de cours d'eau a recu peu d'attention. Nous explorons le lien entre la variabilite temporelle et l'efficacite statistique en utilisant 34 parametres tires de donnees sur des communautes de poissons recueillies annuellement dans six sites, sur une periode de 10 ans, par peche electrique. La variabilite des parametres differe selon l'etape du cycle biologique et le groupe d'especes examines et le type de donnees (abondance ou masse) et la methode de normalisation des donnees utilises. Une plus faible variabilite est associee aux donnees sur les communautes, aux donnees sur l'abondance et aux normalisations basees sur le temps, alors qu'une plus grande variabilite est associee aux donnees sur les jeunes de l'annee, aux donnees sur la masse et aux normalisations basees sur la superficie. L'analyse de l'efficacite basee sur la simulation indique que le choix des parametres et, dans une moindre mesure, le schema de surveillance (annuel, bisannuel, indicateurs d'effet ou echantillonnage a l'aveuglette) influencent l'efficacite de la detection de changements. Pour un nombre fixe de releves (N = 60), l'echantillonnage d'indicateurs d'effet donne les meilleurs resultats. Le N necessaire pour detecter des changements depend fortement du choix des parametres pour tous les schemas de surveillance, les parametres les plus specifiques sur le plan biologique necessitant des N plus grands. D'importantes reductions de l'effort et des ressources depensees peuvent etre obtenues en utilisant des parametres pertinents du point de vue biologique sur lesquels le bruit temporel a peu d'influence, dans un schema d'echantillonnage approprie. [Traduit par la Redaction], Introduction A great deal of time and resources have been devoted to environmental monitoring over the past few decades, yet notably less effort has been devoted to understanding the ability [...]

Objectives for recovery of alosines commonly involve improving fish passage at dams during migration. However, a quantitative basis for dam passage performance standards is largely absent. We describe development of a stochastic life-history-based simulation model for American shad, Alosa sapidissima, to estimate effects of dam passage and migratory delay on abundance, spatial distribution of spawning adults, and demographic structuring in space and time. We used the Penobscot River, Maine, USA, as a case study to examine sensitivity of modeled population metrics and probability of achieving specific management goals to inputs. Spawner abundance and percentage of repeat spawners were most sensitive to survival and migration delay at dams, marine survival, and temperature cues for migratory events. Recovery objectives related to abundance and spatial distribution of spawners were achievable under multiple scenarios, but high rates of upstream and downstream passage were necessary. The simulation indicated trade-offs between upstream and downstream passage efficacy whereby increased downstream passage was required to maintain or increase population abundance in conjunction with increased upstream passage. This model provides a quantitative support tool for managers to inform ecologically based decisions about a suite of management scenarios to facilitate recovery and sustainability of diadromous fish populations. Les objectifs concernant le retablissement d'alosines comprennent souvent l'amelioration du passage de poissons aux barrages durant la migration. Il y a toutefois quasi absence de fondement quantitatif pour l'etablissement de normes de performance de passage de barrages. Nous decrivons l'elaboration d'un modele de simulation stochastique base sur le cycle biologique pour l'alose savoureuse, Alosa sapidissima, afin d'estimer les effets du passage de barrages et le retard de la migration sur l'abondance, la repartition spatiale d'adultes geniteurs et la structuration demographique dans l'espace et le temps. Nous utilisons l'exemple du fleuve Penobscot (Maine, Etats-Unis) comme etude de cas pour examiner la sensibilite aux intrants de parametres demographiques modelises et la probabilite d'atteinte d'objectifs de gestion precis. L'abondance des geniteurs et le pourcentage de geniteurs a reproductions anterieures sont les parametres les plus sensibles a la survie et au retard de la migration aux barrages, a la survie en mer et aux signaux de temperature pour les evenements migratoires. Les objectifs de retablissement associes a l'abondance et a la repartition spatiale des geniteurs sont atteignables pour differents scenarios, mais des frequences elevees de passages en amont et en aval sont necessaires. La simulation indique des compromis entre l'efficacite des passages en amont et en aval, une augmentation des passages en aval etant necessaire pour maintenir ou accroitre l'abondance de la population, de concert avec de plus nombreux passages en amont. Ce modele fournit un outil de soutien quantitatif aux gestionnaires pour eclairer des decisions basees sur l'ecologie concernant un ensemble de scenarios de gestion visant a faciliter le retablissement et la perennite des populations de poissons diadromes. [Traduit par la Redaction], Introduction The American shad, Alosa sapidissima, is an anadromous fish that spawns in the main-stem of coastal rivers on the Atlantic coastal drainage of North America from the St. Johns [...]

Mark-recapture models are widely used to estimate survival of salmon smolts migrating past dams. Paired releases have been used to improve estimate accuracy by removing components of mortality not attributable to the dam. This method is accompanied by reduced precision because (i) sample size is reduced relative to a single, large release; and (ii) variance calculations inflate error. We modeled an idealized system with a single dam to assess trade-offs between accuracy and precision and compared methods using root mean squared error (RMSE). Simulations were run under predefined conditions (dam mortality, background mortality, detection probability, and sample size) to determine scenarios when the paired release was preferable to a single release. We demonstrate that a paired-release design provides a theoretical advantage over a single-release design only at large sample sizes and high probabilities of detection. At release numbers typical of many survival studies, paired release can result in overestimation of dam survival. Failures to meet model assumptions of a paired release may result in further overestimation of dam-related survival. Under most conditions, a single-release strategy was preferable. Les modeles de marquage-recapture sont largement utilises pour estimer la survie de saumoneaux qui franchissent des barrages. Des lachers jumeles ont ete utilises pour ameliorer l'exactitude des estimations en excluant les composantes de mortalite non attribuables au barrage. Cette methode s'accompagne d'une reduction de la precision parce que (i) la taille de l'echantillon est plus faible que pour un seul grand lacher et (ii) les calculs de la variance accroissent l'erreur. Nous avons modelise un systeme idealise comprenant un seul barrage afin d'evaluer les compromis entre l'exactitude et la precision, et compare les methodes en utilisant l'ecart-type (RMSE). Des simulations ont ete realisees pour des conditions predefinies (mortalite due au barrage, mortalite de reference, probabilite de detection et taille de l'echantillon) afin de determiner dans quels scenarios les lachers jumeles sont preferables au lacher unique. Nous demontrons que les lachers jumeles n'offrent un avantage theorique par rapport a un schema de lacher unique que pour des echantillons de grande taille et des probabilites de detection elevees. Pour des nombres de lachers caracteristiques de nombreuses etudes sur la survie, les lachers jumeles peuvent se traduire par une surestimation de a survie apres le passage dans un barrage. Le non-respect des hypotheses sur lesquelles repose le modele pour les lachers jumeles pourrait accroitre encore davantage la surestimation de la survie apres le passage dans un barrage. Dans la plupart des conditions, une strategie de lacher unique est preferable. [Traduit par la Redaction], Introduction Mark-recapture methods are a mainstay for estimating demographic rates and trends in abundance of fish and wildlife populations. Advances in telemetry technology and in statistical-modeling techniques have led to [...]

We developed a hierarchical multistate model to estimate survival of Atlantic salmon (Salmo salar) smolts in the Penobscot River, USA, over a decade during which two mainstem dams were removed from the catchment. We investigated effects of (i) environmental factors, (ii) rearing history, and (iii) management actions, including dam removal, turbine shutdown, and installation of new powerhouses. Mean ± SD smolt survival per kilometre was higher through free-flowing reaches of the catchment (0.995 [+ or -] 0.004 x [km.sup.-1]) than through reaches containing dams that remain in the system (0.970 ± 0.019-[km.sup.-1]). We observed maximum survival between 12 and 17°C and at intermediate discharges (1200 [m.sup.3] x [s.sup.-1]). Smolt survival increased concurrent with dam removal and decreased following increases in hydropower generation. The greatest increase in smolt survival followed seasonal turbine shutdowns at a dam located on the largest tributary to the Penobscot River, while other shutdowns had little influence. Our model provides a useful tool for assessing changes to survival of migratory species and will be useful for informing stocking plans to maximize numbers of smolts leaving coastal systems. Nous avons elabore un modele multi-etats hierarchique pour estimer la survie de saumoneaux de saumon atlantique (Salmo salar) dans le fleuve Penobscot (Etats-Unis) pendant une decennie durant laquelle deux barrages sur le bras principal du fleuve ont ete retires du bassin versant. Nous avons examine les effets (i) de facteurs ambiants, (ii) de l'historique d'elevage et (iii) des mesures de gestion dont le retrait de barrages, l'arret de turbines et l'amenagement de nouvelles centrales electriques. Le taux de survie moyen ± ecart-type par kilometre des saumoneaux etait plus eleve dans les troncons non regules du bassin versant (0,995 ± 0,004 x [km.sup.-1]) que dans les troncons contenant toujours des barrages (0,970 ± 0,019 x [km.sup.-1]). Les taux de survie maximums observes etaient entre 12 et 17°C et a des debits intermediaires (1200 [m.sup.3] x [s.sup.-1]). La survie des saumoneaux a augmente apres le retrait des barrages et diminue apres des augmentations de la production hydroelectrique. La plus grande augmentation du taux de survie des saumoneaux coincidait avec des arrets saisonniers de turbines a un barrage sur le plus grand affluent du fleuve Penobscot, alors que les autres arrets de turbines n'ont pas eu une grande influence. Notre modele constitue un outil pour evaluer les variations de la survie d'especes migratrices et pour eclairer l'elaboration de plans d'empoissonnement dans le but de maximiser le nombre de saumoneaux qui quittent les systemes cotiers. [Traduit par la Redaction], Introduction Atlantic salmon (Salmo salar) stocks in North America diminished beginning in the 1800s, owing to pollution, poor land-use practices, dams, and overfishing (Haines 1992; Parrish et al. 1998). Many [...]

Timing of ocean entry is critical for marine survival of both hatchery and wild Atlantic salmon (Salmo salar) smolts. Management practices and barriers to migration such as dams may constrain timing of smolt migrations resulting in suboptimal performance at saltwater entry. We modeled influences of stocking location, smolt development, and environmental conditions on (i) initiation of migration by hatchery-reared smolts and (ii) movement rate of hatchery- and wild-reared Atlantic salmon smolts in the Penobscot River, Maine, USA, from 2005 through 2014 using acoustic telemetry data. We also compared movement rates in freeflowing reaches with rates in reaches with hydropower dams and head ponds. We compared movement rates before and after (1) removal of two mainstem dams and (2) construction of new powerhouses. Initiation of movement by hatchery fish was influenced by smolt development, stocking location, and environmental conditions. Smolts with the greatest gill [Na.sup.+], [K.sup.+]-ATPase (NKA) activity initiated migration 24 h sooner than fish with the lowest gill NKA activity. Fish with the greatest cumulative thermal experience initiated migration 5 days earlier than those with lowest cumulative thermal experience. Smolts released furthest from the ocean initiated migration earlier than those released downstream, but movement rate increased by fivefold closer to the ocean, indicating behavioral trade-offs between initiation and movement rate. Dams had a strong effect on movement rate. Movement rate increased from 2.8 to 5.4 km x [h.sup.-1] in reaches where dams were removed, but decreased from 2.1 to 0.1 km x [h.sup.-1] in reaches where new powerhouses were constructed. Movement rate varied throughout the migratory period and was inversely related to temperature. Fish moved slower at extreme high or low discharge. Responses in fish movement rates to dam removal indicate the potential scope of recovery for these activities. Le moment de l'entree en mer joue un role cle dans la survie en mer des saumoneaux de saumon atlantique (Salmo salar) tant sauvages qu'issus d'ecloseries. Les pratiques de gestion et obstacles a la migration, tels que les barrages, peuvent restreindre le moment de la migration des saumoneaux, entrainant une performance moins qu'optimale a l'entree en eau salee. Nous avons modelise les influences du lieu d'empoissonnement, du developpement des saumoneaux et des conditions ambiantes sur (i) le debut de la migration par les saumoneaux eleves en ecloseries et (ii) la vitesse des deplacements de saumoneaux eleves en ecloseries et a l'etat sauvage dans le fleuve Penobscot (Maine, Etats-Unis), de 2005 a 2014, a la lumiere de donnees de telemetrie acoustique. Nous avons egalement compare les vitesses de deplacement dans des troncons non regules et des troncons contenant des barrages hydroelectriques et des reservoirs de barrage. Nous avons compare les vitesses de deplacement avant et apres (1) le retrait de deux barrages sur le bras principal et (2) la construction de nouvelles centrales electriques. Le debut des deplacements par les poissons issus d'ecloseries etait influence par le developpement des saumoneaux, le lieu d'empoissonnement et les conditions ambiantes. Les saumoneaux presentant la plus forte activite de la [Na.sup.+], [K.sup.+]-ATPase (NKA) dans les branchies commencaient leur migration 24 heures plus tot que les poissons avec la plus faible activite de la NKA dans les branchies. Les poissons caracterises par la plus importante experience thermique cumulative commencaient a migrer 5 jours plus tot que ceux avec la plus faible experience thermique cumulative. Les saumoneaux relaches le plus loin de l'ocean commencaient a migrer plus tot que ceux relaches plus en aval, mais la vitesse de deplacement quintuplait plus pres de l'ocean, indiquant des compromis comportementaux entre l'initiation et la vitesse des deplacements. Les barrages exercaient une forte influence sur la vitesse de deplacement, cette derniere augmentant de 2,8 a 5,4 km x [h.sup.-1] dans les troncons dont des barrages ont ete retires, mais diminuant de 2,1 a 0,1 km x [h.sup.-1] dans les troncons ou de nouvelles centrales electriques ont ete construites. La vitesse de deplacement variait tout au long de la periode de migration et etait inversement reliee a la temperature. Les poissons se deplacaient plus lentement a debits extremes forts ou faibles. Les reactions au retrait de barrages refletees dans les vitesses de deplacement des poissons indiquent l'ampleur potentielle du retablissement associee a ces activites. [Traduit par la Redaction], Introduction Seaward migration through freshwater and estuarine habitats to ocean feeding grounds represents a critical transition in the life history of anadromous fishes (Zydlewski and Wilkie 2013). In Atlantic salmon [...]

Local realities might differ from the macro perspectives of theories. Moreover, applying theory to local contexts may well lead to wrong conclusions and render the researcher blind to experienced lived worlds. This paper sheds light on the limits of thought and assumptions by analysing qualitative interviews conducted in Kigoma, Tanzania on the topic of witches, witchcraft and witch hunts, and comparing the results with Silvia Federici's neomarxist feminist theory, according to which contemporary witch hunts are linked to the expansion of a capitalist, i.e. neoliberal, world order. As this paper will show, promoting phenomenologically oriented, field-based approaches to theory, Federici's perspective and my own assumptions fail to recognise the ambiguities of witchcraft and to understand the witch as having a moral function within society, rather than being the victim of a concerted attack on the female body; essentially, the witch is a human being that in the perception of the other embodies what an individual in society ought neither to do nor to be. [ABSTRACT FROM AUTHOR]

Through a short literature review and by making use of Heidegger's phenomenological approach and Rosa's theory of resonance in an extensive analysis of semi-structured interviews with students in or close to the Global Studies Programme (GSP), held during the years 2020 and 2021 under pandemic related restrictions, this paper sheds light on opportunities, constrains and particular traits of a digital environment setting in an international and cultural setting and elaborates that a digital study environment was perceived as successful, inspiring and meaningful if interactive relations were fostered; if students heard and felt heard or self-efficient. In this sense, whether or not students met each other physically determined their senses of belonging, their comfort with each other and the success of a digital GSP. Then, students were able to exit their formal roles of being a student in a seminar to which the digital setting tended to reduce them and where inspirational moments could have been rare. It was in such perceived collective moments that knowledge creation and studying was experienced as meaningful, even in a digital setting although alienation was expressed by all interviewees and mutual approachability or equality remained illusive. [ABSTRACT FROM AUTHOR]

Floods can directly affect riverine organisms by displacing them, and population‐level responses to floods can vary depending on flood magnitude and organism mobility. Benthic organisms can resist displacement until substrates become unstable, whereas mobile organisms are generally more resilient. Freshwater mussels are benthic organisms with low mobility, and there is limited research on their population‐level responses to floods. This study provides novel insights to population‐level responses of mussels to large floods (>500 m3/s).Population dynamics (i.e. abundance, survival, and site fidelity) and sampling efficiency (i.e. detection probability) were estimated in a robust design framework for four freshwater mussel species (Cyclonaias petrina, Cyclonaias pustulosa, Amblema plicata, and Tritogonia verrucosa) from 2017 to 2019 at two sites (upper and lower sites) within riffle habitats in the Colorado River, Texas, U.S.A. Individuals of each species were affixed with shellfish tags, with C. petrina and C. pustulosa individuals also being affixed with passive integrated transponder tags. Changes in population dynamics related to the flood event at each site were directly tested. During sampling, a major flood occurred at each of the two study sites; the floods differed in magnitude but were in the 99th percentile of historical flows at their respective gages.There were site‐ and species‐specific differences in estimated abundances, survival, and site fidelity during periods with the floods. Estimated abundances of C. petrina, C. pustulosa, and T. verrucosa were reduced 40–78% by the lesser flood magnitude (1,283 m3/s) at the upper site. Estimated abundances of C. petrina, C. pustulosa, and A. plicata were reduced 93–95% by the greater flood magnitude (4,332 m3/s) at the lower site. There was a reduction in survival of C. petrina at the upper site, while initially high survival at the lower site was reduced during the interval with the flood for all species. Finally, there was a reduction in site fidelity of C. pustulosa at the lower site.Floods reduced the abundance of all species within riffle habitats at the two sites. Large floods, therefore, affect population dynamics of mussels, but the fate of the displaced mussels is unknown, and with limited inference, reach‐scale effects are unknown. This study adds to the growing body of knowledge about responses of aquatic organisms to large floods, although quantification of recolonisation and fate of displaced mussels are needed to fully understand long‐term effects of large floods on mussel communities. [ABSTRACT FROM AUTHOR]