Downstream Migration Research Articles

Downstream Migration Success of Atlantic Salmon Smolts in a River Catchment Highly Fragmented by Hydroelectric Impoundments

ABSTRACTRiverine habitat fragmentation by barriers, including impoundments, is common and their effects on obligate aquatic organisms are manifold. Organisms, such as Atlantic salmon (Salmo salar), that make extensive river migrations are particularly vulnerable to the effects of impoundments. In this study, we use acoustic telemetry to examine the migratory behaviour of Atlantic salmon, as they migrate to sea for the first time as juvenile ‘smolts’, in a river with a series of dams that form a complex hydropower scheme. We demonstrate that overall migration success in the River Dee catchment and particularly through standing waters was remarkably high. We speculate that high migration success in standing waters could be due to relative current speeds providing good quality directional cues to migrants. Migration success past the two dams in this study, was relatively high, although the number of unsuccessful passage attempts before a successful passage was also very high. The vast majority of smolts passed the dams when the turbines were operational. At one dam, smolts did not use an available fish pass but migrated through the generating turbines. These findings provide several routes through which generation could be managed to enhance the success of downstream smolt migration in rivers where there are similar patterns of hydrogeneration in place.

Daily and Seasonal Variation in Downstream Migration of Juvenile Pink Salmon Oncorhynchus gorbuscha (Salmonidae) in Rivers across the Sakhalin and Kuril Region

Daily and Seasonal Variation in Downstream Migration of Juvenile Pink Salmon Oncorhynchus gorbuscha (Salmonidae) in Rivers across the Sakhalin and Kuril Region

Regional and Interannual Variability of the Temporal Characteristics of the Downstream Migration of Juvenile Pink Salmon Oncorhynchus gorbuscha (Salmonidae) in the Rivers of the Sakhalin–Kuril Region

Regional and Interannual Variability of the Temporal Characteristics of the Downstream Migration of Juvenile Pink Salmon Oncorhynchus gorbuscha (Salmonidae) in the Rivers of the Sakhalin–Kuril Region

Quantitative impacts of hydroelectric dams on the trans‐Amazonian migrations of goliath catfish

AbstractHydropower expansion is increasingly responsible for connectivity and biodiversity loss in freshwater ecosystems. The Amazon basin, which supports the highest level of freshwater biodiversity globally, faces such unplanned expansion. Here, we demonstrate and quantify the impacts of two major hydroelectric dams on the Madeira River on the trans‐Amazonian movements of one apex predatory catfish (Brachyplatystoma rousseauxii) performing the longest migration known in freshwaters. Using otolith microchemistry, we show that above the dams, the former basin‐wide homing migration between the breeding grounds in the upper Madeira and the nursery in the Amazon estuary has now been replaced by residency. We found evidence suggesting downstream migration of juvenile fish past dams into the Amazon estuary and that some of them home back to the Madeira. However, we did not find evidence that the fish homing back from the estuary can access their breeding grounds in the upper Madeira; they remain blocked below the dams. Our results provide undisputable evidence that the conservation of the species primarily requires the reestablishment of connectivity with the construction of efficient fishways.

Confinement controls the directional cell responses to fluid forces

Our understanding of how fluid forces influence cell migration in confining environments remains limited. By integrating microfluidics with live-cell imaging, we demonstrate that cells in tightly-but not moderately-confined spaces reverse direction and move upstream upon exposure to fluid forces. This fluid force-induced directional change occurs less frequently when cells display diminished mechanosensitivity, experience elevated hydraulic resistance, or sense a chemical gradient. Cell reversal requires actin polymerization to the new cell front, as shown mathematically and experimentally. Actin polymerization is necessary for the fluid force-induced activation of NHE1, which cooperates with calcium to induce upstream migration. Calcium levels increase downstream, mirroring the subcellular distribution of myosin IIA, whose activation enhances upstream migration. Reduced lamin A/C levels promote downstream migration of metastatic tumor cells by preventing cell polarity establishment and intracellular calcium rise. This mechanism could allow cancer cells to evade high-pressure environments, such as the primary tumor.

Morphodynamics of sine-generated meandering streams under variations of the width-to-depth ratio: A numerical investigation

Meandering is one of the most common planforms of rivers, however, the ecological and fluvial integrity of meandering rivers are under challenges, resulting from increased anthropogenic pressure and extreme climate events. The present study elucidates the morphodynamics of meandering streams under variations of width-to-depth ratio (B/h) by delving into the two dynamic processes underlying within the flow, i.e. cross-circulatory motion and convective redistribution of the longitudinal flow velocity. Series of numerical simulations are performed in 70° sine-generated meandering streams under increasing flow depth that necessitates a wide range of B/h, characterizing flume experiments to large scale natural rivers. The radial flow structures and the early bed deformation patterns are computed and elucidated. Among the classical cross-circulatory flow patterns, outer bank cell occurs for flows having B/h < 9. Next, the different bed deformation patterns reveal the shift of significance in the driving forces of the bed deformation regarding different B/h ratio. At B/h = 100, bed deformation is dominated by the convective redistribution of the downstream velocity that causes longitudinal adjacent erosion–deposition zones. This implies downstream migration tendency of meander loops. At B/h = 12, the intensified cross-circulatory flow deflects the sediment trajectory, causing extra laterally adjacent erosion–deposition zones that necessitate the lateral expansion tendency of the loop. Decrement of B/h ratio (from 100 on ward) critically enhances the non-equilibrium transport of sediment that can lead to active fluvial evolution of meandering rivers. Overall, the results can be used to improve river management and restoration.

Evidence of Secondary Bedform Controls on River Dune Migration

AbstractIn rivers worldwide, multiple scales of dunes coexist. It is unknown how the larger, primary dunes interact with secondary bedforms that are superimposed. We test the hypothesis that streamwise variability in the sediment flux inferred from the downstream migration of secondary bedforms explains migration of the host dune, based on bathymetric data from a lowland, sand‐bedded river. Results indicate that transport estimated from secondary bedform migration increases along the host dune stoss, eroding the stoss slope. When the superimposed bedforms disintegrate at the primary lee slopes, results indicate that all sediment transport associated to secondary bedform migration is arrested in the lee of the host dune, explaining migration of the host dune. When secondary dunes persist however, only part of the sediments transport linked to secondary dunes contributes to the migration of the host dune. This study gives novel insight into the fundamental mechanisms controlling the kinematics of compound dunes.

Impacts of the High-Pressure Bratsk Hydroelectric Power Station on Fish Population of the Bratsk Reservoir

Environmental and ecological effects of the dam of the high-pressure Bratsk Hydroelectric Power Station (HPS) on the fish population and the probability of fish downstream migration from the Bratsk Reservoir have been studied. It has been revealed that thermal stratification of the water column is a significant factor in the ecological differentiation of the fish population in the upper reaches of high-pressure hydroelectric plants. According to hydroacoustics data, most of the ichthyomass, consisting of “warm-water” representatives of the Percidae (65%) and Cyprinidae (22%) families, is concentrated in the relatively warm layer of the epilimnion. Juvenile fish from 30 to 50 mm in size (up to 70% of the total fish number in this layer) are also concentrated here. In the cold-water hypolimnion, the fish population is represented by large single individuals of whitefish (Coregoninae). The data on distribution of fish in the lower and upper reaches of the dam, fish nutrition patterns, growth rate, and the presence of injuries that occur when fish pass downstream through hydroelectric plant dams are presented. Revealed differences in the growth rate of perches from the upper and lower reaches are associated with their constant inhabiting of water masses with contrasting temperatures. Net catches in the lower reaches over the four seasons of research lack injured individuals. These facts prove the absence of mass downstream passage of fish through the Bratsk HPS dam. Juveniles of cyprinids and perches accumulate in the upper warm layer of 0–10 m, i.e. outside the zone of the intake flow formation, which makes their entrance to intake openings at a depth of more than 20 m hardly possible.

The effect of trapping on the migration and survival of Atlantic salmon smolts

AbstractElectronic tags are often used to track the freshwater‐marine migrations of smolts, where smolts are captured for tagging pre‐migration (e.g., via electrofishing) or during‐migration (e.g., via traps). Pre‐migration capture allows smolts to initiate and complete their downstream migration unhindered, but risks smolt loss before the migration commences. The contrary is the case for during‐migration trap‐caught smolts, but trapping smolts temporarily halts their seaward journey which may negatively impact their progress. This study investigated the effect of trapping on the behaviour and survival of migrating Atlantic salmon (Salmo Salar) smolts using acoustic telemetry. We compared the movements and survival of smolts tagged before the smolt run captured by electrofishing (“comparator”) with smolts trapped and tagged during the smolt run (“trapped”). A total of 478 smolts were tagged and released in River Skjern (2020 and 2022), Denmark, and 82 smolts in River Ballycastle (2022), Northern Ireland, and their seaward movements were monitored using acoustic receivers deployed in the river, fjord, and coastal area. In River Skjern in 2022, comparator smolts migrated earlier than trapped smolts, likely because these constituted more of the larger‐sized, earlier migrating individuals. We found no differences in descent trajectories, diel patterns, progression rates, or survival between trapped smolts and comparator smolts in any of the rivers or study years. Thus, our results support the use of during‐migration trapping as a low‐impact method to capture smolts for telemetry studies, with trapped samples (if held &lt;24 h) yielding comparable results in terms of behaviour and survival with non‐delayed pre‐migration tagged fish.

On monitoring the downstream and spawning migrations of Pacific salmon on the Paramushir Island (Northern Kuriles) in 2023

The purpose: The main goal of the work is to study the conditions of migration of juveniles on the control Savushkina River and describe the state of Pacific salmon migrating off the coast of the Paramushir Island in 2023.Methods used: Research work was carried out using standard generally accepted methods.Result: During the research work, data were obtained on the timing and dynamics of migration of juvenile Pacific salmon. The results of monitoring the approaches of Pacific salmon producers are presented. Shown are data on the size-mass characteristics and age composition of chum salmon, sockeye salmon, coho salmon and pink salmon.Practical significance: The results of the research work carried out will be used in the preparation of materials for the projected volume of production (catch) of Pacific salmon for 2024 and subsequent years for the North Kuril subzone.

Recreational fishing in the lower basin of the Santa Cruz river(Patagonia, Argentina) in the face of damming scenarios

The Steelhead ecotype (Oncorhynchus mykiss) and chinook salmon (Oncorhynchus tshawytscha) have promoted a recreational fishery in the Santa Cruz river, the last large free flowing river of Patagonia. However, two dams are being built upstream in the middle course, potentially affecting the life cycle of these anadromous salmonids. The study describes the dynamics of the recreational fishing of the Santa Cruz river around Piedrabuena city and anglers perceptions, discussing its trends according to possible river connectivity scenarios. The fishery was assessed through a monthly year-round field sampling from April 2018 to April 2019, developing instantaneous angler counts, discriminating fishing methods, effort, and catch per unit effort; also, in situ interviews were used to collect information on anglers’ motivations and perceptions. In addition, information on fishing tournaments was used. Three fishing zones (FZ) were identified near Piedrabuena city: FZ-1, located downstream where anglers used baited hook and line to catch the native marine Patagonian blenny (Eleginops maclovinus); FZ-2, located in the town where baited hook and line, spinning, and fly-cast are used to catch Patagonian blenny and salmonids; FZ-3 located upstream the town, where fishing effort was mainly directed to salmonids employing spinning and fly-cast. Fishing effort showed a seasonal pa�ern with high values from March to May and September to October, agreeing with Steelhead and Chinook salmon runs, respectively. The most relevant motivations for anglers were nonoriented catch variables. Anglers preferred the capture of salmonids over native species, considering dams to be a major threat to fishery. Although a postdamming scenario could allow the adult salmonids to migrate upstream, the current reproduction grounds of Steelhead will be flooded, and juveniles and adults of both species will be hindered in their downstream migration to sea. These aspects seem to seriously compromise the future of these unique fisheries.

Computational fluid dynamics simulation of passive downstream fish passage over a weir with OpenFOAM®

Many fish species are dependent on migration through river systems. Weirs are an obstacle to downstream migration, which can lead to obstruction as well as injury and mortality. The current level of knowledge about downstream migration over weirs is limited, and the current assessment of this is uncertain. This study uses a computational fluid dynamics (CFD) method for assessing the damage potential of the downstream migration over the weir, evaluating the effectiveness of the current recommendations. Two test cases were simulated using OpenFOAM® and an interFoam-based solver, extended with Lagrangian particles to represent passively transported fish. The results of the simulations show that adherence to the recommendation for a necessary tailwater level has no significant impact on the relevant hydraulic stressors, shear stress, pressure changes and collisions in certain situations. A thick nappe, however, leads to a significant reduction in collisions, especially of particles initialized near the surface. The CFD method used in this study proves to be suitable for evaluating downstream fish passage with certain limitations. This means that qualitative comparisons of different situations are possible, but not the determination of the damage potential of a specific situation. Further investigations are necessary to identify factors for safe downstream fish passage.

A comparison of acoustic tag sizes on wild Atlantic salmon Salmo salar L. smolt migration success and behaviour

AbstractTracking of animal migrations using telemetry technologies needs to take into consideration the burden that the tag exerts on the animal. Here, we examined the potential impacts of acoustic tags of two sizes (nominally a ‘V6’ [smaller] and ‘V7’ [larger]) on the downstream riverine migration success and behaviour of wild Atlantic salmon (Salmo salar L.) smolts. One hundred fish were tagged with either a V6 or V7 tag. Tag burden (tag: fish weight) ranged from 1.88% to 7.39% and differed significantly between fish tagged with the V6 (mean [SD] = 3.63% [0.51%]) and the V7 tags (mean [SD] = 5.84% [0.95%]). There was no significant difference in the in‐river migration failure between the two groups when tested with a time‐to‐event analysis. There were also no differences in other elements of the migratory behaviour (rate of movement, time of detection and residency time) between the two tagging groups. These data support the use of acoustic tracking for monitoring smolt migration and highlight that tagging of smaller smolts at up to 7.39% tag burden to gain a more representative understanding of migration success and behaviours across a smolt population.

Daily and Seasonal Variation in Downstream Migration of Juvenile Pink Salmon Oncorhynchus gorbuscha (Salmonidae) in Rivers across the Sakhalin and Kuril Region

Daily and Seasonal Variation in Downstream Migration of Juvenile Pink Salmon Oncorhynchus gorbuscha (Salmonidae) in Rivers across the Sakhalin and Kuril Region

Quaternary tectonic and climatic forcing on the spatio-temporal evolution of the Meuse fluvial terrace staircase

The Quaternary is characterized by pronounced alterations between cold and warm climatic states, with the Mid-Pleistocene Transition marking a strong increase in the intensity of cold-climate conditions. River systems are sensitive to environmental perturbation (e.g., climate, tectonics, base level) and are expected to respond to such profound changes. This study uses a combination of terrace mapping and analysis of a dense borehole database to investigate the Meuse terrace staircase (and its deposits), and gain insight on how it reflects climatic and tectonic perturbations during the Quaternary. The lower reaches of the Meuse river, which has both its main water and sediment source in the Ardennes displays a well-developed terrace staircase that was sculpted mainly throughout the Quaternary. The staircase is located near the cities of Maastricht (southern Netherlands) and Liège (northwestern Belgium). About 30 terrace levels reflect signals of environmental perturbations in the lithological composition, gradients, thicknesses, and spatial distribution. The terraces are organized in groups, based on their morphological position, from old to young; these are the East Meuse terrace group and West Meuse High-, Middle- and Low terrace groups. Our findings show a consistent increase in the gravel content from older to younger terraces. The sandier composition of the deposits of the oldest terraces (Early Pleistocene) is closely related to the supply of the Miocene-Pliocene weathered material from the Ardennes. Younger terraces (Middle and Late Pleistocene) are much richer in gravel, evidencing sediment input from fresh or partially weathered bedrock. These changes point to a downstream migration of the gravel front throughout the Quaternary. The mean thickness of the terrace groups shows a slight increase, even though the same trend is not clear when each terrace is analyzed on an individual basis. The anomalous thickness of the Caberg 1 terrace suggests increased sediment input during the cold climatic conditions of the Elsterian (MIS 12), the first Quaternary glacial during which an ice sheet extended into the northern Netherlands. Reconstruction of terrace gradients reveals that older East Meuse terraces show a (reversed) gradient opposite to reconstructed palaeo flow directions, which is attributed to a combination of low gradients during terrace formation and footwall back-tilting of the Feldbiss Fault Zone. In our analysis we do not see clear evidence for the imprint of the Mid-Pleistocene Transition, which suggests that due to its gradual nature, its signal is either buffered or assimilated by the overall climatic signal of the Quaternary. This study offers a first complete temporal analysis of the Meuse terrace staircase, providing an important basis for better understanding the effects of Quaternary climatic change and tectonics, and their resulting effects in other river systems worldwide.

Swimming behaviour of downstream migrating carp in accelerating flows

The downstream migration of fish is impacted by accelerating flow. This study coupled computational fluid dynamics (CFD) modelling and laboratory observations to investigate the effects of two different accelerating flow hydrodynamics on the swimming behaviours of two fish species. The silver carp (Hypophthalmichthys molitrix) and bighead carp (Hypophthalmichthys nobilis) were chosen as target fish species and four hydrodynamic parameters were selected as main indicators to affect fish swimming behaviours. Four specific swimming behaviours were classified in the contraction flume based on fish downstream trajectories. The results indicated that high accelerating flow, low turbulent kinetic energy (Tke ) and shear stress generated the symmetric distribution of fish along two boundaries of the contraction flume. It also indicated that discharge increase would increase the fish entrainment risk from intakes to diversion pipe, while two fish species exhibited different swimming behaviour patterns. Velocity and velocity gradient had more significant effects than other hydrodynamic parameters on fish swimming strategies. There was mutual compensation among fish tail-beat frequency, angle and amplitude. The results illustrated the relationship between the swimming behaviours and hydrodynamics, which could contribute to understanding the fish downstream migration behaviours in accelerating flow.

Ouabain modulates collective cell migration via a Na,K-ATPase activated Ca2+ signal pathway

Collective cell migration is important for many physiological and pathological processes. Ouabain, a cardiotonic steroid and specific ligand to Na,K-ATPase, has been reported to modulate collective cell migration, inhibiting it in cancer cells, and increasing it in normal cells. However, it is not clear what the mechanism is behind this difference in response. It is well-documented that ouabain blocks the pump function of Na,K-ATPase. At low concentrations this activates on the cellular level a Ca2+ mediated signaling chain with multiple downstream effects, including adhesion and migration pathways. At higher concentrations the inhibition of Na+ and K+ transport dominates the effect on the cellular level. We hypothesize that the difference in migration response of cancer and normal cells to ouabain is due to a difference in the Ca2+ signaling response. We further hypothesize that the spread and amplification of Ca2+signals between cells via gap junctions is upregulated by ouabain. To test the hypothesis, we made scratch assays in cultures of MDCK cells and studied migration rate and Ca2+signaling. 10 nM ouabain increases the migration rate, an effect that is inhibited by 2-APB, that blocks the IP3R Ca2+ release from ER. The effect on migration is also blocked by KN-93 that inhibits Ca2+ activated CAMKII. Interestingly, ouabain at 200 nM concentration decreased the migration rate compared to untreated cells. To analyze the strength of intercellular communication we analyzed the spread and synchronicity of spontaneous Ca2+ signals between neighboring cells. For this we used MDCK cells stable transfected with the Ca2+ sensitive fluorescent protein GCamp6f. Cells were treated with vehicle, ouabain 10 nM, or heptanol (blocks gap junctions). Timelapse Ca2+ imaging for 10-30 minutes was done. Machine learning based image analysis with Cellpose was then used to segment cells, followed by cross correlation of the integrated Ca2+signals from neighboring cells. Despite findings from previous phosphoproteomic studies indicating that there should be an upregulation of gap junctions, no conclusive differences in intercellular signaling could be identified for the different treatments. Finally, we made high resolution imaging of cells immunolabeled for vinculin and FAK, two proteins that are involved in migration and adhesion. We found ouabain correlated effects on the localization of vinculin and FAK with a polarized and concentrated localization after high dose ouabain, compared to a diffuse and unpolarized localization after low dose ouabain. Taken together we suggest that low dose ouabain via Na,K-ATPase triggers a Ca2+ signal that destabilize cell adhesions and that this is an important mechanism contributing to the observed upregulation of cell migration. Marta and Gunnar V Philipson's foundation, and VR 2020-05347 (Swedish Research Council). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Downstream passage performance of silver eel at an angled rack: effects of behavior and morphology

The European eel is critically endangered due to heavy impact of anthropogenic factors, such as habitat fragmentation, overexploitation and climate change. During downstream migration, silver eels may encounter hydropower plants, which often result in delay or mortality from impingement on trash-racks or turbine passage. These problems can be mitigated with downstream passage solutions, such as angled racks that guide downstream-migrating eels to safe passage routes. The importance of bar spacing and phenotypic diversity for passage performance is, however, largely unknown. In this study, we investigated how morphological parameters (body mass, eye and fin indices) and behavioral score (open field test) influenced passage rate at an experimental intake equipped with a bypass and angled racks with either 15 or 30 mm bar spacing. Both racks were efficient in guiding eels into a bypass. There was a strong positive effect of body mass and a weak positive effect of open field test score on passage rate. Other factors such as eye and fin indices played a minor role. These results demonstrate the performance of angled racks with bypasses and form a useful starting point for further research regarding the relationships between individual variation in behavior, morphology and passage solutions for silver eels.

Thermal conditions in the marine coastal waters as a factor favorable for formation of extra-strong year-classes of Karaginsky pink salmon

Variability of the timing for downstream migration of juvenile pink salmon from the Hailulya River to the adjacent coastal waters of Karaginsky Bay is considered and influence of the coastal water temperature on strength of the year-classes for two generative lines of pink salmon spawning in the Karaginsky Bay is analyzed for 1978–2020. The optimal conditions for the downstream migration in the period after 2002 are determined as the mean weighted per migration intensity water temperature &gt; 5.6 o C (up to 7.8 о С on average with the maximum 9.9 о С in some years) and a stable increasing of the temperature during migration. The factor of food availability for juveniles became less important for formation of the Karaginsky pink salmon year-classes since the late 2000s, in comparison with the temperature. Statistical model is proposed for the year-class strength dependence on the temperature of coastal waters in late June and the parents number (R2 = 0.791). The modeled hindcasts of the pink salmon returns in 2021–2023 were rather satisfactory. Given these new results, the limits of pink salmon escapement to spawning grounds could be reconsidered and fishery management models should be adjusted to modern conditions of unrestricted juvenile feeding to get and rationally exploit super-strong year-classes of this species.

Approach to the Hydraulics of Orifices to Fish Bypasses for Downstream Migration

Approach to the Hydraulics of Orifices to Fish Bypasses for Downstream Migration