While interspecific competition is prevalent in natural systems, we do not yet understand how it can influence an individual’s phenotype within its lifetime and how this might affect performance. ...Morphology and swimming performance are two important fitness-related traits in fishes. Both traits are essential in acquiring and defending resources as well as avoiding predation. Here, we examined if interspecific competition could induce changes in morphology and affect the swimming performance of two strains of juvenile Atlantic salmon (Salmo salar). We imposed competitive scenarios on the fish using artificial streams containing different combinations of four interspecific competitors. Exposure to interspecific competitors induced morphological changes over time, through the development of deeper bodies, whereas controls free of interspecific competitors developed more fusiform body shapes. Furthermore, swimming performance was correlated to fusiform morphologies and was weaker for Atlantic salmon in competitive scenarios vs. controls. This implies that interspecific competition has direct effects on these fitness-related traits in Atlantic salmon. To the best of our knowledge, this is the first time that morphology, an important fitness-related trait linked to swimming performance, has been shown to be negatively impacted through interactions with an interspecific competitor.
Identifying early gene expression responses to hypoxia (
, low dissolved oxygen) as a tool to assess the degree of exposure to this stressor is crucial for salmonids, because they are increasingly ...exposed to hypoxic stress due to anthropogenic habitat change,
, global warming, excessive nutrient loading, and persistent algal blooms. Our goal was to discover and validate gill gene expression biomarkers specific to the hypoxia response in salmonids across multi-stressor conditions. Gill tissue was collected from 24 freshwater juvenile Chinook salmon (
), held in normoxia dissolved oxygen (DO) > 8 mg L
and hypoxia (DO = 4‒5 mg L
) in 10 and 18° temperatures for up to six days. RNA-sequencing (RNA-seq) was then used to discover 240 differentially expressed genes between hypoxic and normoxic conditions, but not affected by temperature. The most significantly differentially expressed genes had functional roles in the cell cycle and suppression of cell proliferation associated with hypoxic conditions. The most significant genes (n = 30) were selected for real-time qPCR assay development. These assays demonstrated a strong correlation (r = 0.88;
< 0.001) between the expression values from RNA-seq and the fold changes from qPCR. Further, qPCR of the 30 candidate hypoxia biomarkers was applied to an additional 322 Chinook salmon exposed to hypoxic and normoxic conditions to reveal the top biomarkers to define hypoxic stress. Multivariate analyses revealed that smolt stage, water salinity, and morbidity status were relevant factors to consider with the expression of these genes in relation to hypoxic stress. These hypoxia candidate genes will be put into application screening Chinook salmon to determine the identity of stressors impacting the fish.
Abstract
When operating in Speed-No-Load (SNL), turbines function at their synchronous rotating speed with a fraction of discharge at best efficiency point, ready for electrical grid connection. The ...flow in SNL condition is characterized by high swirling component leading to complex flow structures inside the runner, which generate wide-band pressure fluctuations. When operating in SNL condition, high specific speed turbines, such as axial turbines, can be damaged by significant pressure oscillations attributed to rotating vortex phenomena, alike rotating stall. However, understanding the fundamental flow dynamics behind the phenomena in SNL condition remains challenging due to the stochastic nature of flow. The present research highlights unsteady flow characteristics and flow instabilities in SNL condition of a bulb turbine by URANS simulations based on scale-resolving techniques. The simulation results provide evidence that the development of a rotating vortex array in precession with the runner is a major source of pressure oscillations and torque fluctuations in SNL operation of this bulb turbine.
Abstract
In hydraulic turbines, no-load operation is among the most damaging conditions since unextracted swirl leads to the creation of highly energetic flow structures causing high pressure and ...strain fluctuations on the turbine components. To date, experimental and numerical studies typically focus on flow characteristics for a specific no-load condition of a specific turbine. However, for a given turbine, a unique no-load condition exists for every single guide vane opening, forming what is called a no-load curve. Few studies describe the evolution of engineering quantities such as discharge and speed along the no-load curve even if those quantities may highlight trends in no-load behavior that can be used to tailor numerical simulations according to specific flow conditions. This paper presents results from a project underway at Andritz Hydro Canada Inc., in collaboration with Université Laval, to analyze the extensive database of experimental no-load tests performed at model scale in order to identify the evolution of discharge and runner rotation speed following the guide vane opening.
Theory predicts that hybrid fitness should decrease as population divergence increases. This suggests that the effects of human-induced hybridization might be adequately predicted from the known ...divergence among parental populations. We tested this prediction by quantifying trait differentiation between multigenerational crosses of farmed Atlantic salmon (
Salmo salar
) and divergent wild populations from the Northwest Atlantic; the former escape repeatedly into the wild, while the latter are severely depleted. Under common environmental conditions and at the spatiotemporal scale considered (340 km, 12 000 years of divergence), substantial cross differentiation had a largely additive genetic basis at behavioral, life history, and morphological traits. Wild backcrossing did not completely restore hybrid trait distributions to presumably more optimal wild states. Consistent with theory, the degree to which hybrids deviated in absolute terms from their parental populations increased with increasing parental divergence (i.e., the collective environmental and life history differentiation, genetic divergence, and geographic distance between parents). Nevertheless, while these differences were predictable, their implications for risk assessment were not: wild populations that were equally divergent from farmed salmon in the total amount of divergence differed in the specific traits at which this divergence occurred. Combined with ecological data on the rate of farmed escapes and wild population trends, we thus suggest that the greatest utility of hybridization data for risk assessment may be through their incorporation into demographic modeling of the short- and long-term consequences to wild population persistence. In this regard, our work demonstrates that detailed hybridization data are essential to account for life-stage-specific changes in phenotype or fitness within divergent but interrelated groups of wild populations. The approach employed here will be relevant to risk assessments in a range of wild species where hybridization with domesticated relatives is a concern, especially where the conservation status of the wild species may preclude direct fitness comparisons in the wild.
The three dimensional unsteady swirling flow inside the draft tube of a bulb turbine is investigated using time-resolved stereoscopic particle image velocimetry. The measurement plane located inside ...the conical diffuser, together with synchronous pressure measurements from thirteen sensors distributed across the draft tube, allow to link the draft tube flow dynamics to a known efficiency drop of the turbine. This paper presents the experimental setup and the first observations based on statistical analyses and instantaneous snapshots of the velocity field. After the efficiency drop, the intermittency and skewness of the draft tube pressure recovery are found to be reflected onto the velocity fields. Spectral analysis reveals the presence of a coherent and non-axisymmetric structure that rotates at the same frequency as the runner, but in the opposite direction.
This paper presents a study of the inception mechanism of a rotating stall instability identified on a model propeller turbine during speed-no-load (SNL) operation. It seeks to understand the origins ...of columnar vortices dominating the flow in the runner in SNL. It is based on the use of an experimentally validated flow simulation strategy using the SAS turbulence modelling approach. Two sets of boundary conditions were used to identify the onset of the columnar vortices and confirm that they are linked with a boundary layer separation on the turbine head cover.
The effect of deafness on sensory abilities has been the topic of extensive investigation over the past decades. These investigations have mostly focused on visual capacities. We are only now ...starting to investigate how the deaf experience their own bodies and body-related abilities. Indeed, a growing corpus of research suggests that auditory input could play an important role in body-related processing. Deafness could therefore disturb such processes. It has also been suggested that many unexplained daily difficulties experienced by the deaf could be related to deficits in this underexplored field. In the present review, we propose an overview of the current state of knowledge on the effects of deafness on body-related processing.
Steady state and non-linear harmonic (NLH) flow simulations were performed within the framework of the Francis-99 project in order to assess the capacity of the NLH method to capture the main ...pressure fluctuations associated with the rotor-stator interactions between the distributor and the runner of the turbine. This paper focusses on the methodology developed to obtain harmonic solutions and presents preliminary results from the simulations using the flow solver NUMECA FineTURBO on intermediate grid level meshes. Comparisons of the first simulations to experimental data reveal good agreement concerning the predicted pressure amplitudes notably at high load operating condition.
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