Search Results (98)

The placement of hydraulic elements in existing pool-type fishways to make them more suitable for Cyprinid fish is an issue of increasing interest in fishway research. Hydrodynamic characteristics and fish behavior at the representative pool of the fishway with bottom orifices and notches were assessed at the Dagdelen hydropower plant in the Ceyhan River Basin, Türkiye. Three-dimensional velocity measurements were taken in the pool of the fishway using an Acoustic Doppler velocimeter. The measurements were taken with and without a brush block at two different vertical distances from the bottom, which were below and above the level of bristles tips. A computational fluid dynamics (CFD) analysis was conducted for the studied fishway. The numerical model utilized Large Eddy Simulation (LES) combined with the Darcy–Forchheimer law, wherein brush blocks were represented as homogenous porous media. Our results revealed that the relative submergence of bristles in the brush block plays a very important role in velocity and Reynolds shear stress (RSS) distributions. After the placement of the submerged brush block, flow velocity and the lateral RSS component were reduced, and a resting area was created behind the brush block below the bristles’ tips. Fish movements in the pool were recorded by underwater cameras under real-time operation conditions. The heatmap analysis, which is a 2-dimensional fish spatial presence visualization technique for a specific time period, showed that Capoeta damascina avoided the areas with high turbulent fluctuations during the tests, and 61.5% of the fish presence intensity was found to be in the low Reynolds shear regions in the pool. This provides a clear case for the real-world ecological benefits of retrofitting existing pool-weir fishways with such flexible hydraulic elements. Full article

Effective monitoring of fish passage through river barriers is essential for evaluating fishway performance and supporting adaptive river management. Traditional methods are often invasive, labor-intensive, or too costly to enable widespread implementation across most fishways. Infrared (IR) beam-break counters offer a promising alternative, but their adoption has been limited by high costs and a lack of flexibility. We developed and tested a novel, low-cost infrared beam-break counter—FishTracker—based on open-source Raspberry Pi and Arduino platforms. The system detects fish passages by analyzing interruptions in an IR curtain and reconstructing fish silhouettes to estimate movement, direction, speed, and morphometrics under a wide range of turbidity conditions. It also offers remote access capabilities for easy management. Field validation involved controlled tests with dummy fish, experiments with small-bodied live specimens (bleak) under varying turbidity conditions, and verification against synchronized video of free-swimming fish (koi carp). This first version of FishTracker achieved detection rates of 95–100% under controlled conditions and approximately 70% in semi-natural conditions, comparable to commercial counters. Most errors were due to surface distortion caused by partial submersion during the experimental setup, which could be avoided by fully submerging the device. Body length estimation based on passage speed and beam-interruption duration proved consistent, aligning with published allometric models for carps. FishTracker offers a promising and affordable solution for non-invasive fish monitoring in multispecies contexts. Its design, based primarily on open technology, allows for flexible adaptation and broad deployment, particularly in locations where commercial technologies are economically unfeasible. Full article

Hydropower infrastructure has profoundly altered riverine connectivity, posing challenges to the migratory behavior of aquatic species. This study examined the post-passage migration efficiency of Schizothorax wangchiachii in a regulated river system, focusing on upstream and downstream reaches of the Songxin Hydropower Station on the Heishui River, a tributary of the Jinsha River. We used radio-frequency identification (RFID) tagging to track individuals after fishway passage and coupled this with environmental monitoring data. A Cox proportional hazards model was applied to identify key abiotic drivers of migration success and to develop a predictive framework. The upstream success rate was notably low (15.6%), with a mean passage time of 438 h, while downstream success reached 81.1%, with an average of 142 h. Fish exhibited distinct diel migration patterns; upstream movements were largely nocturnal, whereas downstream migration mainly occurred during daylight. Water temperature (HR = 0.535, p = 0.028), discharge (HR = 0.801, p = 0.050), water level (HR = 0.922, p = 0.040), and diel timing (HR = 0.445, p = 0.088) emerged as significant factors shaping the upstream movement. Our findings highlight that fishways alone may not ensure functional connectivity restoration. Instead, coordinated habitat interventions in upstream tributaries, alongside improved passage infrastructure, are crucial. A combined telemetry and modeling approach offers valuable insights for river management in fragmented systems. Full article

Vertical slot fishways (VSFs) are crossing devices that are built on rivers or streams. They were initially designed to help salmons to complete their migratory cycle by crossing permanent obstructions. In order to favor the passage of smaller or benthic species, stones or concrete cylinders, called macro-roughnesses, are often inserted at the bottom of the fishway. To study the effects of macro-roughnesses on the flow inside a VSF, three-dimensional unsteady simulations were carried out using the volume of fluid method to model the free surface. In this paper, kinematic quantities obtained by CFD are used to detail the flow inside a VSF with and without macro-roughnesses. It can provide valuable information about the flow characteristics, especially in areas where the experimental measurements are difficult to implement. Full article

To help fish to bypass dams and other human-made barriers, some fishways have ingeniously incorporated extended tunnel sections. This innovative design not only optimizes the overall structure of the fishway but also significantly reduces disturbances to the surrounding ecosystem. However, the potential challenges posed by long tunnel sections to fish upstream migration remain insufficiently studied and poorly understood. This study conducted in situ experiments utilizing a passive-integrated-transponder (PIT) system to quantitatively assess the effects of dark and natural light environments on the upstream migration behavior of plateau-endemic fishes (Schizothorax macropogon, Schizothorax waltoni, and Schizothorax oconnori) in a vertical-slot fishway. A 655 m section of the fishway was selected for the experiment, with shading cloth used to simulate the dark environment (DE) of tunnel sections, and its removal serving as the natural light environment (NE). The results showed that in the DE, the upstream behaviors of S. macropogon, S. waltoni, and S. oconnori were not hindered. The entry efficiency at the experimental segment (Ee) of all three species exceeded 65% in the DE, which was higher than that in the NE. The passage efficiency (Ep) of S. macropogon and S. waltoni showed no significant difference between the DE and NE, whereas S. oconnori exhibited a significant difference, with an overall Ep of 0% in the NE and 75.0% in the DE. Additionally, the DE caused a temporary disruption to the diel migration rhythms of the three species. The transit speeds (St) of S. macropogon and S. waltoni were both elevated in the DE, with S. waltoni showing a particularly significant increase; its average St in the DE (0.080 m/s) was much higher than in the NE (0.021 m/s). Ridge regression analysis further indicated that the DE was the primary factor influencing the St and had a positive effect on upstream behavior. Moreover, differences in the upstream migration performances of different species under varying light conditions highlighted species-specific sensitivity to light. This study offers key insights for fish passage design in canyon hydropower projects and highlights the potential of tunnel-type fishways in restoring river connectivity. Full article

The vertical slot fishway (VSF) has proven effective in mitigating the severe fragmentation of rivers caused by artificial hydraulic structures. While fishways with steeper slopes exhibit better economic performance, increased slope can raise the flow velocity and turbulence, which may hinder fish migration. To address this issue, this study investigated the application of a VSF with a staggered baffle configuration. Through numerical modeling, the hydraulic characteristics of the VSF under various slope ratios and chamber length-to-width (L/B) ratios were investigated, with data validated by physical models. An increase in the slope gradient resulted in higher flow velocities, greater maximum attenuation rates of mainstream velocity, and elevated turbulent kinetic energy (TKE) at the corners of the rectifier baffles and the ends of the divider baffles. Additionally, the overall maximum volumetric energy dissipation ($D_{\epsilon }$) increased, although its distribution pattern remained unaffected. Conversely, increasing the chamber L/B ratio significantly altered the distribution patterns of the flow velocity, TKE, and $D_{\epsilon }$, influencing their generation mechanisms. For instance, a higher chamber L/B ratio caused the maximum flow velocity (V_m) to deviate from the vertical slot and raised the maximum attenuation rate of the mainstream velocity. The L/B ratio also caused changes in the TKE distribution; as the ratio increased, the proportion of the chamber’s internal region with $D_{\epsilon }\le 150 \mathrm{W}/{\mathrm{m}}^3$ initially decreased and then increased. Overall, considering the flow velocity, TKE, and $D_{\epsilon }$, it is recommended that the chamber L/B ratio be maintained between 0.9 and 1.1 for slope ratios ranging from 1:20 to 1:50. The research results will offer practical insights for engineering applications, in engineering construction, contribute theoretical guidance for the optimized design of fish passages, promote sustainable hydraulic engineering practices, and aid in the protection of aquatic biodiversity. Full article

Fishways can effectively validate the effectiveness and rationality of their construction, optimize operational modes, and achieve intelligent scientific management through fish species detection. Traditional fish species detection methods for fishways are unsuitable due to inefficiency and disruption of the fish ecological environment. Therefore, combining cameras with target detection technology provides a better solution. However, challenges include the limited computational power of onsite equipment, the complexity of model deployment, low detection accuracy, and slow detection speed, all of which are significant obstacles. This paper proposes a fish detection model for accurate and efficient fish detection. Firstly, the backbone network integrates FasterNet-Block, C2f, and an efficient multi-scale EMA attention mechanism to address attention dispersion problems during feature extraction, delivering real-time object detection across different scales. Secondly, the Neck introduces a novel architecture to enhance feature fusion by integrating the RepBlock and BiFusion modules. Finally, the performance of the fish detection model is demonstrated based on the Fish26 dataset, in which the detection accuracy, computational cost, and parameter count are significantly optimized by 1.7%, 23.4%, and 24%, respectively, compared to the state-of-the-art model. At the same time, we installed detection devices in a specific fishway and deployed the proposed method within these devices. We collected data on four fish species passing through the fishway to create a dataset and train the model. The results of the practical application demonstrated superior fish detection capabilities, with rapid detection ability achieved while minimizing resource usage. This validated the effectiveness of the proposed method for equipment deployment in real-world engineering environments. This marks a shift from traditional manual detection to intelligent fish species detection in fishways, promoting water resource utilization and the protection of fish ecological environments. Full article

Fishways are an important solution for mitigating the ecological impacts of river barriers, with their hydrodynamics playing a key role in their effectiveness. Computational fluid dynamics (CFD) is now one of the main tools to predict and characterize flow hydrodynamics, but choosing the most suitable turbulence model is considered one of its main challenges. Although substantial research has been carried out on vertical slot fishways, where the flow is predominantly two-dimensional, studies on pool-type fishways with bottom orifices remain scarce. In this study, three Reynolds averaged Navier–Stokes (RANS) turbulence models (the standard k-ε model, the renormalized group k-ε (RNG) model, and the standard k-ω model) and the large-eddy simulation (LES) model performances were compared to simulating the flow in a pool-type fishway with bottom orifices. ADV and PIV experimental data were used to assess model performance. While all the turbulence models accurately predicted the discharges and flow depths, the LES model outperformed the others in reproducing flow patterns, velocities, and turbulent kinetic energy. The RNG model also showed reasonable agreement with the experimental data. By contrast, the k-ε model delivered the poorest performance, failing to accurately predict the sizes of the recirculation zones and the locations of the recirculation axis and presenting the weakest agreement with the experimental observations. The value of the LES model in studying and characterizing fishway hydrodynamics, particularly concerning turbulence parameters, is highlighted. Full article

Innovating seal structures and optimizing size parameters are effective ways to enhance the leakage characteristics of labyrinth seals (LSs). Inspired by the ecological fishways with high flow resistance on dam sides, a novel bio-inspired staggered labyrinth seal is proposed. The leakage characteristics of both the curved-edged bio-inspired labyrinth seal (CELS) and the straight-edged bio-inspired labyrinth seal (SELS) at different tooth-incline angles are studied numerically and experimentally. The influence of key geometrical parameters on the leakage characteristics and flow field parameters of the CELSs are investigated, and the leakage control mechanism of bio-inspired LSs is revealed via analyzing flow field parameter distribution. The results indicate that, compared to conventional double-sided staggered straight-tooth labyrinth seals, the leakage rate reduction in CELSs is up to 30% when the incline angle is equal to 25°, outperforming that of the SELS in leakage control. This improvement is mainly attributed to the flow path bending and jet contraction effects at the tooth-tip entrance, along with the thermodynamic effects of the high-turbulence dissipation zone adjacent to the tooth top. The optimum leakage characteristics can be achieved when seal clearance h < 0.5 mm, aspect ratio δ < 0.6, and tooth thickness t < 1.5 mm. This work provides new insights into the structural design of high-resistance and low-leakage labyrinth seals. Full article

Dams severely affect aquatic environments and block the longitudinal migration of fish. In order to mitigate the negative effects generated by these developments, fish passes, or fishways, are implemented in dams with the purpose of restoring river connectivity and allowing the movement of migrants. Nevertheless, fishways in neotropical areas often face design and construction issues that can reduce their efficiency and selectively disadvantage species with limited swimming capabilities. This study analyzes how a fish ladder on the Paraná River influences the black armored catfish (Rhinelepis aspera), a benthic, long-distance migratory species important to commercial fisheries. A total of 200 individuals were PIT-tagged and monitored for four months. The results showed that although many fish successfully located the fishway, only a small portion (3.5%) managed to complete the ascent. The interaction between the hydraulic characteristics of the fishway and the fish condition factor played a significant role in ascent performance. Our findings underscore the importance of assessing fishway suitability for benthic neotropical species to support conservation efforts in the Upper Paraná River Basin. To improve passage rates for R. aspera, we recommend optimizing flow conditions by adjusting orifice and notch configurations, incorporating roughness elements, and modifying resting pool designs. These adaptations would reduce energy expenditure for ascending fish, enhancing fishway performance and contributing to the sustainability of migratory species in this region. Full article

Fishways act as ecological corridors, enabling migratory fish species to surmount barriers such as weirs or dams, which are crucial for the restoration of river ecosystems. The island-type fishway is a novel design that utilizes a combination of island structures and valvular configurations to dissipate the kinetic energy of water flow, decelerate the water velocity, and thus reduce the challenge faced by fish attempting to ascend the watercourse. The impact of valvular configurations on the hydrodynamic characteristics within an island-type fishway was explored. The results showed that the main high-velocity flow exhibits a nearly “S”-shaped characteristic, while a low-velocity region develops downstream of the valvular. The valvular configuration has a significant effect on the internal flow dynamics of the island-type fishway. Specifically, the smaller the valvular arc angle, the broader the high-velocity main flow becomes, and the smaller the area of the low-velocity region. When the valvular arc angle is set at 180°, the area dominated by low flow velocities maintains a coverage of over 60%. As the valvular arc angle decreases, turbulent kinetic energy rises, leading to an approximate 70% increase in the maximum turbulent kinetic energy across different water layers relative to the model with the initial angle setting. Within the range of valvular arc angles studied, an island-type fishway with a 180° valvular arc angle is most conducive to supporting the upstream migration of fish. This study can provide a reference for the further development of island-type fishways. Full article

The present study explores the strategic siting of hydroelectric power plants, focusing on the Miyanaka Intake Dam (MID) and Shinano River Hydroelectric Power Station (SHP). Built in 1939 to support Tokyo’s railway electrification, these facilities demonstrate the complexities of balancing renewable energy production with ecological conservation. Despite the high costs and energy losses associated with transmitting power from the Sea of Japan side, the SHP has effectively powered Tokyo’s rail system for over 80 years, owing to advanced transmission technologies and the region’s abundant water resources. However, river-crossing structures such as dams disrupt fish migration and habitats, necessitating the implementation of fishways. The MID fishway, continually improved since its construction, emphasizes the importance of integrating ecological considerations into hydropower projects. Our findings highlight the higher power generation efficiency on the Sea of Japan side and stress the need for careful site selection to ensure sustainable hydroelectric power while preserving river ecosystems. In conclusion, hydropower sites should be chosen based on both environmental impacts and future development potential to maintain the ecological balance and support long-term renewable energy goals. Full article

Fish passage facilities are essential for restoring river connectivity and protecting ecosystems, effectively balancing economic and ecological benefits. Systematic and comprehensive monitoring, assessment, and optimized management are therefore crucial. This study quantitatively evaluated the entire upstream migration process of fish from the downstream river to the entrance and exit of the fishway and investigated the upstream movement patterns of fish under various environmental factors. A total of 19 fish species were monitored in the Heishuihe River downstream of the dam, with 15 species reaching the fishway entrance and 12 species successfully passing through it. The entrance attraction and passage rates of the vertical-slot fishway at the Songxin hydropower station were 15.7% and 40.42%, respectively. The best upstream performance was observed in May, with fish demonstrating better upstream timing and speed during nighttime compared to daytime. Specifically, the highest entrance attraction efficiency was recorded at a flow rate of 6–7 m³/s and a temperature of 19–20 °C, while the optimal passage efficiency was observed at a flow rate of 0–0.5 m³/s and a temperature of 17–20 °C. Additionally, a multifactorial Cox proportional hazards regression model was constructed to identify key factors influencing the probability of fishway entrance attraction and successful passage. The model elucidated the impact patterns of these key factors on fish upstream migration, ultimately generating an alignment diagram for prediction and control. This study provides a theoretical foundation and data support for developing optimized operational schedules for fishways. The findings offer a more comprehensive and systematic approach for monitoring and evaluating fish passage facilities, serving as a scientific basis for ecological restoration and fish conservation in this region and similar areas. Full article

The hydrodynamics at the fishway entrance play an important role in attracting fish into a fishway. Adjusting the entrance angle of the fishway to allow suitable water flow patterns at the entrance is an effective measure that can be used to improve the attraction efficiency. In this study, we analyzed the movement behavior of grass carp (Ctenopharyngodon idella) in a river channel at a fishway entrance with different fishway entrance angles (30°, 45°, and 60°) and different replenishment velocities (0.1 m/s, 0.2 m/s, and 0.3 m/s). The flow velocity was 0.32–0.50 m/s when the fish head deflected into the entrance under different entrance angles for grass carp. As the entrance angle of the fishway increased, the fish energy consumption increased. The range of energy consumption for grass carp increased from 1.26–3.59 × 10⁻³ J to 3.32–7.33 × 10⁻³ J when the entrance angle was increased from 30° to 60°. There was a negative correlation between the entrance angle of the fishway and the deflection angle of the tested fish’s head. This research presents a reference that combines fish swimming behavior and hydraulics to optimize the design of fishway entrances. Full article

Dams fragment stream habitats and fishways around dams typically serve few species that are strong swimmers or jumpers. We tested a prototype wetted ramp designed to allow upstream passage of small-bodied fishes while blocking upstream movement of invasive sea lampreys in the Laurentian Great Lakes. We tested short, smooth ramps with 5–10 mm water depth in various combinations of ramp angle, water flow, and swim channel width with the aim to selectively block adult migrating sea lampreys (Petromyzon marinus) while passing sub-adult white suckers (Catostomus commersonii) and creek chubs (Semotilus atromaculatus). Sea lampreys easily passed a 0.75 ramp at a 5° angle, but very few individuals passed a similar ramp at a 10° angle, and none passed a longer ramp at a 5° angle. Limiting the amplitude of tailbeats in a narrow channel did not hamper lampreys or the other species. Greater water flow, and thereby greater immersion depth on the ramp, fostered passage for all species. Smaller-bodied individuals of creek chubs and white suckers performed best on the ramp. We showed that wetted ramps could be incorporated into fishways at low-head dams to aid the passage of smaller-bodied fishes while also blocking the spawning migration of adult sea lampreys. Full article