Passage Facilities Research Articles

A coupled machine-learning-individual-based model for migration dynamics simulation: A case study of migratory fish in fish passage facilities

The extensive development of hydropower projects has notably changed the ecohydrological conditions of fish habitats, affecting fish behavior, including habitat usage and migration, to varying extents. Understanding fish migration dynamics is essential for quantitatively assessing the impact of ecological restoration measures on migratory fish. However, no model has yet demonstrated sufficient accuracy to be considered valuable in ecological restoration engineering. To address this issue, in this article, a coupled machine-learning-individual-based model (ML-IBM) consisting of random forest (RF) and Eulerian–Lagrangian–agent method (ELAM) is constructed for predicting fish migration, aiming to find effective fish passage solutions before implementation. In this study, the passage data of ya-fish (Schizothorax prenanti) in vertical slot fishways (VSFs) is compiled to train ML-IBM to simulate fish migration in fish passage facilities. In movement prediction, the accuracy of swimming behavior classification reaches 83.4 %, and the R² for swimming speed regression exceeds 0.77. Compared with other state-of-the-art migration dynamic models, the proposed ML-IBM achieves the lowest root mean square error (RMSE) of 7.35 and a mean absolute error (MAE) of 6.26 in migration simulation results. Further, RF is used to quantitatively calculate the importance of input features. The contributions of each feature are analyzed and discussed from a hydrodynamic perspective, with the importance ranked as follows: flow velocity (FV) > turbulent kinetic energy (TKE) > total hydraulic strain (THS). This approach enhances the interpretability of the model and provides further insights into the mechanism of fish migration. The results presented in this study have significant implications for informing decision-making in the management of living resources and guiding engineering design processes.

Impact of Hydropower on River Biodiversity and Strategies for Recovery

Hydropower significantly contributes to global renewable energy but also poses serious challenges to river biodiversity. This paper examines the ecological impacts of hydropower, such as changes in hydrological regimes, habitat fragmentation, migration barriers, and water quality degradation. It also explores various recovery strategies, including environmental flow management, habitat restoration, fish passage facilities, and community-based conservation initiatives. Case studies like the Elwha River restoration and the Aswan High Dam illustrate lessons learned and the necessity of integrating scientific, policy, and community efforts to sustain river ecosystems alongside hydropower development. This research underscores the balance needed between renewable energy benefits and ecological preservation.

Quantitative Assessment and Regulation of Passage and Entrance Attraction Efficiency of Vertical-Slot Fishway on Heishuihe River in Southwest China.

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.

Effects of hydraulic cues in barrier environments on fish navigation downstream of dams

Understanding how hydraulic cues in the barrier environment affect fish navigation is critical to fish migration in dammed rivers. However, most of the current research on the effects of hydraulic cues on fish navigation focuses on the effects of a single hydraulic parameter on fish migration and usually ignores fish sensory perception and swimming ability. This study presents an effective approach that combines a computational fluid dynamics model of a river with a model of fish behaviour to elucidate the effects of hydraulic cues in the barrier environment on fish migration paths and strategies by simulating the fish's perception of flow direction and their regulation of multiple hydraulic parameters. Four release scenarios for the dam were reviewed and it was determined that the modelled fish movements realistically reflected actual observations. In various scenarios, the target fish (Schizothorax chongi) managed to move upstream to the tailrace downstream of the dam, despite the hydraulic barrier created by the mainstem area of the river; they overcame this obstacle by exploiting low-velocity zones on both sides of the mainstem and in the river's boundary layer. During upstream movement, the target fish preferred areas with flow velocities between 0.7 and 1.0 m/s and a turbulent kinetic energy of less than 0.3 m2/s2 to maintain aerobic activity. Additionally, the effects of alternative turbine release strategies on the fine-motor movement of target fish were reviewed and an optimised strategy was provided that could increase the proportion of target fish entering the fish passage facility from 0% to 53.8% in the original scenario to 82.6%. This study provides a feasible method for the simulation of fish fine motion in complex flow environments as well as a scientific basis for the management of fish resources in dammed rivers.

Managing water gate operation and fish passage facilities in irrigated systems of the Nam Kam River, Thailand

AbstractThe migration of fishes through the Thoranit Naruemit water gate on the Nam Kam River, a tributary of the Mekong River in Thailand, was studied to understand the hydrological factors and improve the operational regime of the fish pass at the structure. Migration of fish from the Mekong River started in May, at the onset of the rainy season. During 60 days of operation, the fish pass supported the upstream migration of 83 species and ~440,000 fish, equivalent to about 11 tonnes of fish. The fish pass supported migration of a range of fish sizes between 45 and 700 mm, and most fish were larger than the size of first maturity for the species in question. The factors influencing migration into the Nam Kam included the lunar cycle, flow in the fish pass, water level in the river and flow variability. Migration tended to increase in the 3–4‐day period before or after a full moon. Discharge and water level changes associated with rising water levels in the Mekong River synchronize with the spawning season of most Mekong fish and trigger upstream migration. Many fish migrated through the pass at discharges through sluice gates between 8 and 323 m3/s and with a flow through the fish pass between 0.95 and 3.08 m/s. Restrictions to fish migration were found and recommendations for water gate and fish pass operation are provided.

A design of a nature-like fishway to solve the fractured river connectivity caused by small hydropower based on hydrodynamics and fish behaviors.

Achieving a harmonious alignment between the biological characteristics of fish and hydrodynamics patterns is crucial for ensuring the efficacy of fish passage facilities. In this study, based on the hydrodynamic characteristics of the river and the biological characteristics of fish, we evaluated the internal flow field in the nature-like fishway of Congen II hydropower station located along the Chabao river and explored methods to improve the operation efficiency. Based on comprehensive considerations of the flow field, turbulent kinetic energy, and the migration pathways of fish, it is found that the implementation of a continuous oblique bottom slope represents a more cost-effective and operationally convenient solution. The influence of different permutation of bulkheads in the nature-like fishway on operational efficiency was further examined. Our investigation revealed that the nature-like fishway with the continuous slope of 2% and the arrangement of three bulkheads in each row (model 3) exhibited a relatively simple velocity distribution and linear flow line, which poses challenges for fish in locating resting areas. In addition, the distribution of low turbulence kinetic energy area in the mainstream made it less favorable for fish to transition from the mainstream to the rest area within the fishway. The nature-like fishway with the continuous slope of 2% and the arrangement of two or three bulkheads in staggered rows (model 4) demonstrated better performance. Several potential fish migration routes for both model 3 and model 4 were proposed based on the numerical simulation results. In model 3, fish exhibited a continuous sprint through the concentrated high-speed area, which was less favorable for fish to rest and forage. In contrast, model 4 exhibited a diversified flow velocity distribution, enabling fish to make timely changes in their direction during migration. This feather proved to be advantageous in enhancing fish migration within the passage. The design of nature-like fishway in this study provides an important reference and technical support for the construction and optimization of the nature-like fishway for low dams, and is of great significance for restoring river connectivity destroyed by small hydropower construction and improving fish migration.

PIT tagging systems are suitable for assessing cumulative impacts of Mekong River hydropower plants on (upstream) fish migrations in Lao PDR

The Mekong River has the largest inland fishery in the world but is threatened by planned mainstem hydropower developments that could impact fish migration patterns. Here we provide direct evidence of long-distance migrations along the Mekong mainstem by Hypsibarbus malcomi, one of the 10 most important species in the Mekong River fishery. The migration included a 354 km passage through one current and three proposed hydropower developments. We tagged and released 233 wild fish, including 77 H. malcomi with Passive Integrated Transponder (PIT tags) near the capital Vientiane in April of 2022. Five PIT tagged H. malcolmi were detected at the top of the Xayaburi hydropower plant fish ladder within 15 months of being released at Vientiane. Our findings empirically demonstrate that this species undertakes long distance migrations in the main stem of the Mekong and therefore that suitable fish passage facilities will need to be incorporated in mainstem hydropower developments to meet their migratory needs. The findings also demonstrate the value of including a fishery independent and efficient monitoring technology, such as PIT tagging, to assess the migration patterns of fish in the face of upcoming developments in the Lower Mekong Basin.

The Eel Ascending: The Influence of Lateral Slope, Climbing Substrate and Flow Rate on Eel Pass Performance

Optimising the design of passage facilities to restore fluvial connectivity for juvenile European eel (Anguilla anguilla) is a key priority within conservation efforts for the species, across the majority of its freshwater range. Employing an experimental setup that simulated gravity-fed upstream eel passes, this study demonstrated that novel V-profile passes, which incorporate two lateral slopes (15°), performed better than laterally flat passes over the flow rates tested (0.2–0.6 L s−1). For the small eel size used (60–80 mm length), the bristle substrate consistently outperformed studs, but the lateral slope had a greater effect on passage metrics than the substrate choice. Our findings strongly support the use of V-shaped channels for upstream migrating eel at fish passage facilities, particularly in scenarios where flow rates may be elevated and/or fluctuating, such as for gravity-fed passes.

Assessing migratory bottlenecks and escapement of silver eel (Anguilla anguilla) in the highly urbanized North Sea Canal basin, the Netherlands

AbstractHabitat fragmentation and migration barriers have attributed to the decline of European eel (Anguilla anguilla). The migration of silver eels through pumping stations, ship locks, and migration facilities within the North Sea Canal basin using acoustic telemetry and overall escapement by mark–recapture was studied. A network of 61 acoustic receivers and three PIT‐tag stations was built, and 305 silver eels were tagged with acoustic transmitters and 3923 with PIT‐tags. Of all the silver eels that were detected, 55% passed barriers between the polders and the canal and 46% also passed the barrier complex at IJmuiden to sea, mainly via the ship locks. Overall, silver eel escapement to the North Sea per year averaged 81,629 silver eels and 14.3% suffered mortality in the pumping station at IJmuiden. Migration speed was lower for silver eels that initiated their migration upstream compared with silver eels further downstream, higher for silver eels passing barriers later in the migration period, and highest at sea. This study of silver eel movement and escapement in the North Sea canal basin indicated several bottlenecks. Passage success along barriers varied strongly between sites and types of barriers. While at two smaller locations, silver eels migrated through the pedal valves in the ship lock gates, a small passage facility and the pedal valves in a ship lock at complex IJmuiden did not enhance silver eel migration. The barriers and unnatural canal system caused additional delay during silver eel migrations. Mitigation measures for management could include installing fish‐friendly pumps, using pumping stations only during the day, and in addition opening ship locks and pedal valves at the beginning of the night.

Adult Sea Lamprey approach and passage at the Milford Dam fishway, Penobscot River, Maine, United States

AbstractObjectiveSea Lamprey Petromyzon marinus provide important ecological services within their native range, such as nutrient cycling, and can also act as a prey source for other species. Adult Sea Lamprey must access freshwater rivers to spawn, and because of this they are susceptible to changes in river connectivity. Human‐made structures, such as dams, can exclude them from usable habitat. Sea Lamprey dam passage has not been extensively studied in Maine, despite Maine being within the native range of this species. The goals of this study were to evaluate upstream passage efficiency at the Milford Dam on the Penobscot River, Maine, and to provide comprehensive information about adult Sea Lamprey passage at five other dams throughout the Penobscot River watershed.MethodsIn 2020–2021 we captured and tagged 150 Sea Lamprey at the Milford Dam, the lowest dam in the Penobscot River, Maine, and displaced them downstream to assess passage efficiency at this dam and five upstream dams. In 2020, 50 Sea Lamprey were released on the east shore of the river downstream of Milford Dam; in 2021, the east shore release was repeated with an additional 50 fish and another 50 fish were released on the west shore.ResultBetween 70–82% of Sea Lamprey were observed passing Milford Dam again after mean delay times of 9–11 days. The release location did not affect dam passage success or the amount of time that was required to locate and use the passage structures. Sea Lampreys from both release groups were equally likely to approach the entrance to the fishway upon returning to Milford Dam, despite the fishway being located against the eastern shore of the river. However, high flows shortly after release may have resulted in higher attraction to the fishway in 2020. Passage success at dams upstream of Milford was highly variable. All Sea Lamprey were able to successfully navigate past West Enfield Dam (100% passage, n = 63), whereas Brownsmill Dam apparently acted as a complete barrier to further migration (0% passage, n = 7). Fish from all years and release groups together had a median upstream migration distance of 38.8 km after fish had passed Milford Dam, and a maximum observed upstream travel distance of approximately 100 km, indicating that most tagged Sea Lamprey ended their migration in the vicinity of a dam.ConclusionThe results of this study indicate that Sea Lamprey have high passage efficiency at the Milford Dam and highlight areas within the Penobscot River basin—such as the Brownsmill Dam—where passage facilities are currently inadequate for Sea Lamprey.

Restoration of a fish-attracting flow field downstream of a dam based on the swimming ability of endemic fishes: A case study in the upper Yangtze River basin

The construction of fish passage facilities can mitigate the negative effects of dams and other water engineering construction on river connectivity and have a significant positive effect on the conservation of local fish diversity. To attract target fishes into fish passage facilities effectively, the optimal flow velocity range to attract fish must be determined. Three local endemic species of the Mishi Reservoir were considered as the protection targets. However, their swimming abilities remain unclear. Therefore, the induced swimming speed (Uind), critical swimming speed (Ucrit) and burst swimming speed (Uburst) of three fish species were tested. Based on these results, we identified the optimal flow velocity to attract fish, which falls within the range of 0.15–0.51 m/s. A validated three-dimensional hydrodynamic model was used to simulate different schemes. By comparing the flow field simulation results of different schemes, we obtained the optimal measure to restore the flow field, namely, a multiple engineering measure combining increased the fish attraction flow in the fish collection pond and the construction of a spur dike. This study offers a solution for the specific case and enhances the database of swimming characteristics of endemic fish in the upstream reaches of the Yangtze River. It also provides a valuable reference for designing fish-attracting flows and potential measures for restoring flow fields in similar future projects.

Application of Vortex Identification Methods in Vertical Slit Fishways

The reproduction and survival of fish are often negatively affected by the construction of dams and other hydroelectric projects, which cut off their migratory routes. Building effective fish passage facilities that allow fish to pass through dams smoothly alleviates the negative impact of hydroelectric projects on the ecological environment, thus protecting the diversity of aquatic species and preventing the extinction of indigenous fish. Vertical slit fishways are highly effective, but turbulence inside the fishway pools directly affects fish passage. In this study, the large-eddy simulation framework is used to capture the vortex characteristics in the interior of vertical slit fishway pools, and the volume of fluid method is applied to simulate the free surface. The independence of the grid is assessed by the large-eddy simulation quality index, and the simulation results are compared with experimental acoustic Doppler velocimetry data. This work characterizes the vortex flow field inside the vertical slit fishway using the Q-criterion, Omega method, and Liutex vortex identification method. The results show that the vortex structure inside the fishway pool has obvious three-dimensional characteristics and vortex structure varies within the different fishway pool chambers. The analysis and comparison of the three different vortex identification methods show that the vortex structure captured by the Liutex method is more consistent with the actual motion pattern of the fishway water flow.

Adaptation and Resilience

In times of social and environmental changes, water and wastewater utilities provide the foundations for their communities so they can focus on growing and improving. But to remain (or become) sustainable, utilities must themselves grow and improve, and they can do so generally through two approaches: adaptation and resilience. If the wind blows harder, the reed can either adapt to bend more easily, or it can grow stronger and bury its roots deeper to resist breaking. Water systems are unique in that they can use both approaches at the same time, strengthening certain areas of management and operations, while others evolve in response to new perspectives and technologies. Highlighting areas of sustainable water management, this month's Journal AWWA has articles on resource management, source water protection, and the development of alternative supplies and partnerships. Partnerships and collaboration can further a utility's sustainability goals. Our cover story focuses on one example of this—when Des Moines Water Works faced significant source water quality challenges, its utility staff adapted by collaborating with a range of organizations to better protect its water supplies and ultimately its customers. Another article shows how improving water reliability in Washington's South Puget Sound helped aquatic species and increased community water resilience; the complex financial and permitting issues related to a fish passage facility and an additional water supply project were ultimately overcome by collaborating with like-minded organizations to build widespread support. Focusing more on novel technologies and approaches, another story this month shows how utilities can protect their customers and water distribution system operations by using the US Environmental Protection Agency's EPANET program to model water age. The model results can help utilities adapt how they design, operate, and optimize their distribution systems. The final feature in this month's issue describes how utilities need advanced technologies and new analytical approaches to develop alternative water supplies. As more utilities incorporate reverse osmosis in their treatment processes, advanced membrane forensics can identify the causes of membrane fouling, assess membrane condition, and determine ways to optimize the system to improve resilience and save money. This issue demonstrates how the principles of sustainable water are reflected in practice around the industry. But as all these examples show, water systems have a never-ending responsibility to their communities, and continuity and dedication are necessary to make them sustainable now and in the future. Taking a holistic approach by collaborating across an entire community benefits everyone. Join in the collaboration and share your innovative projects or sustainable approaches. Consider writing an article for Journal AWWA by contacting me at journaleditor@awwa.org.

Reproductive ecology of muskellunge (Esox masquinongy), an introduced predator, in the lower Wolastoq/Saint John River, New Brunswick, Canada.

Introduced predators can have harmful top-down effects on their newly colonized system through competition with and direct predation on native species. Following an initial introduction of muskellunge in Lac Frontière, Québec in the 1970s at the headwaters of the Wolastoq/Saint John River, the species rapidly migrated downstream, expanding its range by ~500 km over ~20 years. Despite this expansive colonization and concern over possible threats to native species, little is known about the basic ecology of muskellunge in this system. The last downstream barrier is the hydroelectric facility, Mactaquac Generating Station (MGS), 150 km upstream of the sea. While there are no downstream fish passage facilities at MGS, adult muskellunge have been recorded downstream. In this study, muskellunge (n= 23) were surgically tagged with very-high-frequency (VHF) radio or combined acoustic radio telemetry (CART) tags and tracked over two spawning seasons. We sought to determine if there was a reproducing population downstream of MGS and tracked Tagged muskellunge over two spawning seasons. We tracked fish to locate and confirm spawning sites, and followed up with egg and/or juvenile sampling surveys. Tagged muskellunge (90%) moved upstream towards the MGS during the spawning period in each year (2016 and 2017), where they remained throughout the entire spawning period. No spawning or nursery sites were confirmed near MGS, but in 2016 three distinct spawning locations and six distinct nursery sites were confirmed 10-12 km downstream amongst a chain of flooded islands. In 2016, eggs, sac-fry and juveniles were collected and confirmed as muskellunge by genetic sequencing, providing the first empirical observation of successful spawning downstream of MGS.

Three-dimensional migratory behaviour of European silver eels (Anguilla anguilla) approaching a hydropower plant.

The global population of European eel (Anguilla anguilla) is rapidly declining, and migration barriers in rivers are believed to be one of several key causes. While progress has been made in the development of bypass solutions, they are often constructed based on a limited knowledge of swimming behaviour. A bypass close to the stream bed is often recommended at fish passage facilities to accommodate downstream eel migration. The results of this recommendation are poorly studied, and the few studies that exist show varying bypass efficiencies. The current study used acoustic telemetry with depth sensors to explore the three-dimensional migratory behaviour of downstream-migrating silver eels. The eels were tracked as they approached a hydropower plant with a state-of-the-art angled bar rack and full-depth bypass. Downstream and upstream swimming differed in preferred vertical and lateral positions. During periods of local downstream movement, the density of observations was largest in the upper middle section, away from the river boundaries and in higher velocities. Conversely, when moving upstream, eels tended to avoid the upper layers of the middle part of the river, swimming closer to the riverbed and using the bank areas to a greater extent. Downstream-moving fish swam higher in the water column during night and in turbid conditions (high discharge). When approaching the impassable bar rack and the full-depth bypass, the eels searched most intensely but not exclusively along the bottom third of the rack, often exploring at new depths after changing direction. The impediment passage efficiency was 100% when both bypass solutions were considered. The study provides knowledge of the swimming behaviour of silver eels, which is relevant for the design of bypass solutions for eels at migration barriers.

Optimization schemes to significantly improve the upstream migration of fish: A case study in the lower Yangtze River basin

The construction of fish passage facilities is a promising approach to balance fish conservation and water resource development by improving river connectivity. To be successful, a fishway must efficiently attract fish to its entrance and have an interior flow field that meets the needs of migrating fish. In this paper, methods were explored to improve the efficiency of fishway passages by optimizing the flow field near the fishway entrance and the flow field inside the fishway in a case study at the Niuling Reservoir in the lower Yangtze River basin. The original engineering design was modified by designing a unique retaining wall with a notch to shape the appropriate flow pattern near the fishway entrance. The new wall optimized the flow field near the fish entrance to meet the hydraulic demands of target fishes under three operating scenarios, and the area of the suitable velocity zone increased by 48.79%, 12.71%, and 4.06% in scenarios 1 through 3, respectively. The original vertical slot fishway was modified with a sill to optimize the flow field inside the fishway. The optimized fishway design scheme reduced the main flow velocity inside the fishway to a large extent, and the maximum flow velocity in the upstream and downstream sections of the fishway decreased by 0.10 m/s and 0.09 m/s on average, respectively. The results of this study provide an important reference for the construction and optimization of fish passage facilities and have great significance for fish migration and biological diversity.

Seasonal migration and habitat use of adult barbel (Barbus barbus) and nase (Chondrostoma nasus) along a river stretch of the Austrian Danube River

Migration patterns and habitat use of adult barbel (Barbus barbus) and nase (Chondrostoma nasus) were monitored by radio telemetry over a period of 13 months along a 58-km-long section of the Austrian part of the Danube River. The study site is confined upstream and downstream by two hydropower plants, and contains a larger tributary, the Pielach River. Telemetry transmitters were implanted into fish caught in this tributary after spawning in June (25 individuals per species). The results show that both species use the entire available width and depth spectrum of the Danube along the full migratable river length. Nase had an average home range of 22.4 km, while that of barbel was 34.4 km. The habitat use of the two species differs significantly. While the nase was primarily encountered in the free-flowing section, barbel mainly used deep areas of the impoundment during the year. Nase showed a distinct site fidelity to certain areas in the free-flowing reach which were periodically revisited. During the spawning season, distinct homing behavior was observed in both species. All seven nase that could still be detected during the spawning season returned to the tributary (homing rate 100%). Six homing nase migrated up to the first migration barrier in the tributary but did not pass the existing fish passage facility. In contrast, only nine barbel returned to spawn in the tributary (homing rate 50%), while nine barbel were most likely using a spawning location in the head of impoundment section. Homing fish entered the tributary during darkness.

Optimizing fish-friendly flow pattern in vertical slot fishway based on fish swimming capability validation

Vertical slot fishways are increasingly common structures for the passage of a wide variety of migratory fish species, which account for 59.2% of all fish passage facilities in China. The slot structures and redirected flow in the pools are of great importance to guide the fish to swim through the fishway. To optimize the design of vertical slot fishways, physical experiments and numerical simulations were used to study the hydraulic characteristics for 10 different geometric configurations (referred to as designs D1-D10), combining with the study of fish behavior in the model. A comparative study on vertical slot fishway with L-shaped baffle (D1) and with a new vertical baffle (D2) was conducted. Flow patterns, velocity fields and other key hydraulic parameters including the maximum velocities and turbulence kinetic energy in the pools were analyzed. No obvious differences in all key hydraulic between designs D1 and D2 present in the study, which suggests an upgrade of the L-shaped baffle to the new vertical baffle with the advantage of being more compact and economical. When modifying design D2 in the baffle thickness and length (D3-D10), three typical flow patterns with the different area ratios of left recirculation region to right recirculation region (Scl/Scr) were observed in the pools, which were denoted as flow pattern 1 (FP1), flow pattern 2 (FP2) and flow pattern 3 (FP3). An analysis of the behavior of grass carp (Ctenopharyngodon Idella) in the scaled model clearly showed that the flow and structure in FP2, with the principal flow in the center position and suitable velocity gradient and recirculation area ratio, were more friendly to fish with better migrating efficiency, which present sufficient velocity gradient and area of cushion zone for migratory fish to pass with less energy consumption.

Determining the position of a fish passage facility entrance based on endemic fish swimming abilities and flow field.

Hydropower development can significantly mitigate climate change and reduce carbon emissions, but it can also have substantial negative impacts on river environments and fish biodiversity. Fish passage facilities are built to ensure sustainable hydropower development and the biodiversity of fish populations. The locations of the entrances to these facilities play a key role in their efficiency. This study presents a reliable approach that combines the swimming ability of fish and a numerical flow field simulation to determine the optimal location for a fish passage facility entrance. In this study, we used the Gujun Reservoir upstream of the Yangtze River as a case study. A field experiment was conducted, and the swimming abilities of eight endemic fish species in the upstream region of the Yangtze River were measured. Among the tested species, the fastest induced swimming speed (0.14m/s) was achieved by Glyptothorax sinense, while the slowest critical swimming speed (0.30m/s) was observed for Paracobitis potanini. We propose that the velocity near the fish passage facility entrance should be higher than the maximum induced swimming speed and lower than the minimum critical swimming speed, making the suitable range between 0.14 and 0.30m/s. On this basis, velocity fields 500m downstream of the dam of the Gujun Reservoir under 4 operating conditions with discharge flows of 5.7 m3/s, 23.3 m3/s, 32.5 m3/s, and 41.1 m3/s were calculated. The results showed that the flow field variation downstream of the dam was between 0.1 and 0.9m/s. After comparing the suitable areas for the target species, the left bank at location 2 was recommended as the optimal location for the fish passage facility entrance in the Gujun Reservoir.

Analysis of Movements and Behavior of Bighead Carps (Hypophthalmichthys nobilis) Considering Fish Passage Energetics in an Experimental Vertical Slot Fishway.

Simple SummaryHydraulic structures have modified the natural waterways, and they have inevitably blocked fish migration routes and reduced fish habitat. To mitigate the impact on fish, fish passages have been developed as an effective way to restore riverine connectivity. The design of fish passage facilities refers to both hydrodynamics and fish behavior, and the information on the energetic expenditure of fish can be used to identify movement zones that are suitable for fish migration. Thus, this paper intended to identify fish movement behavior in response to water flow field information by means of estimating the energetic expenditure using an IBM approach. The results demonstrated that the fish required more energy in high TKE zones, and they were therefore likely to utilize the low TKE zones. This study provides a reference for optimizing the design of fish passages, and the method can be applied to assess the efficiency of fish passages and other fish bypass structures.An understanding of fish movement behavior in response to flow field variables is important for exploring the hydrodynamic strategies of fish in fish passages. In this paper, bighead carps were taken as an example. The fish movement behavior response to water flow field information by means of estimating the energetic expenditure using an IBM approach in an experimental fishway was investigated. Fish swimming velocity, drag force, and energy expenditure were analyzed in varied flow conditions related to hydraulic variables, including velocity (V), turbulent kinetic energy (TKE), and strain rate (SR). The result indicated that the fish will require more energy in high TKE zones. This study provides a reference for optimizing the design of fish passages and fisheries management. This method can be applied to assess the efficiency of fish bypass structures and conduct fish survival studies.