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Fish biodiversity assessments are vital for understanding threats and aquatic ecosystem health. In the Poso River, Central Sulawesi, changes in biodiversity are influenced by habitat alteration, non-native species, and overfishing. This study evaluates fish and crustacean biodiversity in the Poso River system to address these challenges for improving fisheries management, conservation, and fish passage integration into hydropower development. The present biodiversity study utilized a comprehensive methodology that encompassed both traditional taxonomic approaches and DNA barcoding, specifically targeting the mitochondrial cytochrome c oxidase subunit-1 (COI) gene for accurate species identification and spatial boundary validation. The survey was conducted in the upstream, hydropower area and downstream areas of the river. We found 27 species of fish in the Poso River, including both native (e.g., Anguilla celebesensis, Oryzias nebulosus, Rhyacichthys aspro) and non-native species (e.g., Melanochromis auratus, Amphilophus trimaculatus, Oreochromis niloticus). Two International Union for Conservation of Nature (IUCN) red listed endangered species were also observed (e.g., Adrianichthys poptae and Mugilogobius sarasinorum). DNA barcoding was performed to examine species spatial boundaries. The fish population in the Poso River was dominated by non-native species, accounting for 85.70% of the total population. The upstream reaches had the highest fish abundance and diversity, while the downstream reaches had the lowest. There was, however, no significant difference in species richness and diversity across different locations and seasons. The dominance of non-native species in the Poso River necessitates the improvement of existing fishways within the hydropower dams potentially through the development of selective technology that can block the distribution of these non-native species. This research highlights the critical issue of non-native species proliferation and the potential threat they pose to native fish populations, providing valuable insights for conservation and management efforts in Indonesia and similar ecosystems worldwide. [ABSTRACT FROM AUTHOR]

Understanding and improving passage by diadromous species at tidal barriers is less well advanced than that for non-tidal anthropogenic river barriers. This study assessed factors affecting upstream passage of anadromous river lamprey (Lampetra fluviatilis) at a tidal weir with pool-and-weir (PAW) and bypass (BP) fishways. A Continuous Time Markov Model (CTMM) was used to analyse migration behaviours of 120 acoustic- and PIT-tagged lamprey across 2 years. The weir was a major barrier to upstream migration with a mean time of 31.0 days taken to pass the weir compared to 2.5 days for the unobstructed reach immediately downstream. River stage was the most important variable associated with weir passage, with a 5.68 (CI = 3.95, 8.17) increase in passage probability for every 1 m river stage increase. Passage was predominately over the weir directly rather than by the fishways. Monitoring the fishways using additional PIT-tagged lamprey (n = 2814) suggested poor entrance efficiency (BP2018, 28.6%; BP2019, 53.1%; PAW2018, 37.0%). Successful fishway passage was estimated as 5.4% (BP2019)–9.0% (PAW2018) of lamprey that entered. Effective fishway entrance for lamprey is probably facilitated by high fishway discharge, yet high-velocity areas may have made it difficult for river lamprey to successfully ascend the fishways. [ABSTRACT FROM AUTHOR]

Swimming ability and performance are central to the ecology of aquatic species and to the design of structures intended to promote access to habitat. This is particularly important for migratory species traveling over significant distances. Here, we present results of a study of swimming behaviors of adult shortnose sturgeon (Acipenser brevirostrum). Sturgeon were presented with velocity challenges of 0.5–2.5 m·s‒1 in a 35 m long flume that they were allowed to enter and ascend volitionally. Attempt rate was greatest among large sturgeon, at warm temperatures, and at low flow velocities. Sturgeon swam for shorter distances and durations against high-velocity flows; larger sturgeon had greater overall performance and endurance, but when velocities were standardized to body lengths the relative performance was reduced with increased body size. Overall, however, sturgeon were able to swim at much greater speeds than previously predicted, consistent with other studies showing that volitional performance exceeds that of data collected in common laboratory apparatus. [ABSTRACT FROM AUTHOR]

The pool-type fishway, such as pool-weir, vertical-slot, and rock-weir fishways, is one of the most common fishways that presented the highest efficiency for all fish species. Understanding the flow hydrodynamics inside the fishway is crucial to elicit the fish responses and improve passage for multiple species. This review paper summarizes and discusses the main findings of different research studies on the hydraulics of vertical-slot type technical and rock-weir type nature-like fishways under experimental, numerical, and natural conditions. This paper discusses the effects of geometric characteristics on the pools' flow patterns, flow regimes, depth-discharge relationships under uniform and non-uniform flow conditions, and maximum velocity prediction methods that are encountered. This review paper synthesizes the long-term advancement of flow hydraulics in vertical-slot and rock-weir fishways, which ultimately will help engineers and fish biologists involved in the design of fishways. [ABSTRACT FROM AUTHOR]

A challenge in the design of fishways especially for large rivers is the trade‐off between attraction and passability of the entrance. High flow velocities in the entrance slot generate a strong attraction flow and tend to have better attraction efficiency for upstream migration. However, these velocities may also prevent small‐bodied species or juvenile fish from entering the fishway. With our experiment, we reproduced fish swimming behaviour and passage of a fishway entrance for small‐bodied fish under realistic hydraulic conditions. At an entrance slot with 0.4 m width four velocities 0.8, 1.2, 1.5 and 1.8 ms−1 were investigated. In total, 326 juvenile roach (Rutilus rutilus (Linnaeus, 1758)), gudgeons (Gobio gobio (Linnaeus, 1758)) and spirlins (Alburnoides bipunctatus (Bloch, 1782)) were tested. The passage rates of the three tested species were altogether higher than would have been predicted from reported swimming capacities. They increased from gudgeons to roach and (significantly) to spirlins and we could show how passage rates of the three species decreased with increasing flow velocities, suggesting species‐specific critical slot velocities. Still, these velocities are lower than those currently proposed to generate sufficient attraction flow, which may have implications for fishway design. [ABSTRACT FROM AUTHOR]

A fishway is an engineered structure designed to help fish navigate past artificial barriers in rivers such as dams, weirs and regulators. An effective fishway design requires an understanding of fish biodiversity and migration requirements of the local community.To support the conceptual design of a fishway at Caringin Weir in the Cibareno River in Indonesia, we conducted a fish biodiversity assessment using experimental fishing and an eDNA metabarcoding survey.In early 2022, experimental fishing was conducted at six sampling sites upstream and downstream of the planned weir, and the sites were surveyed seven times during the wet and dry seasons. Environmental DNA sampling was conducted once during the wet season at each of the six sites.A total of 72 aquatic species were detected, comprising 40 fish species and seven crustacean species captured during experimental fishing and 36 fish species identified through eDNA metabarcoding. Twelve fish species (18.46%) were detected using both methods. The total number of all species caught and species richness in experimental fishing varied significantly between upstream and downstream areas (p < 0.05), but there were no significant differences between seasons (p > 0.05). There was also a significant difference in the species richness upstream and downstream using eDNA metabarcoding (p < 0.05). There were also numerous diadromous species, further highlighting the need for an effective fishway design to enable these species to complete their migrations.Based on the species present, migratory behaviour and economic importance, we prioritised six fish and crustacean species to be considered during fishway design: Anguilla marmorata, Tor tambra, Barbodes binotatus, Sicyopterus sp., Rhyacichthys aspro and Macrobrachium sp. [ABSTRACT FROM AUTHOR]

The Yarlung Zangbo River (YZR) on the Tibetan Plateau is a prime hotspot for hydropower development in China, yet this inevitably poses risks to river connectivity and the survival of its unique endemic fish species. Fishway installations are often adopted to mitigate the impacts on fish, but their effectiveness especially in high-altitude regions remains inadequately studied. Our study offers the first comprehensive evaluation of a fishway installed on a primary tributary of the YZR from 2019 to 2021, using multiple methods including fish sampling, video monitoring, hydroacoustic detection, and passive integrated transponder telemetry technology. The below-dam fish community was dominated by cold-water rheophilic Schizopygopsinae, Schizothoracinae, and Nemacheilidae. Fish movements exhibited distinct seasonal and diel patterns, with activity rising in April and peaking in May. Approximately 75.0 % of fish movements within the fishway were recorded during daytime (7:00–19:00), whereas the fish assemblage near the fishway entrance primarily occurred during nighttime (20:00–6:00). Telemetric trials on five endemic species revealed upstream- and downstream passage efficiencies of 31.0 % and 61.7 %, respectively. Passage efficiency, transit time, and speed varied substantially among species and individuals, primarily affected by environmental factors such as fishway discharge and water temperature. Our findings provide the essential information on fish behavior and movement patterns for designing more effective fishways in plateau regions and underscore the importance of continuous monitoring and evaluation to optimize fishway performance, ensuring that the conservation of endemic fish species is achieved successfully amid expanding hydropower development in the region.

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. [ABSTRACT FROM AUTHOR]

This paper presents the hydraulic and structural design of a hydraulic jump stilling basin over a rough bed using three-dimensional, unsteady, detached-eddy simulation (DES). The concept design is related to a stilling basin downstream of a 50 m high dam. The use of a rough bed reduces the stilling basin length and depth, compared to the smooth bed scenario, avoiding the use of baffle blocks or dentated sills as suggested in the literature and guidelines, such as U.S. Bureau of Reclamation (USBR). The aim of this paper is to extend recent theoretical analysis on hydraulic jump over a rough bed to real-life dam cases and compare the result with the classical smooth bed stilling basins. The information related to the application of Computational Fluid Dynamics (CFD) to hydraulic jump stilling basins over rough beds is limited, and this paper provides novel results on the internal characteristics of the hydraulic jump over rough beds as well pressure fluctuations coefficients, spatial correlation function, and coefficient of lift. The CFD results are validated using available experimental and theoretical information. A step-by-step guide is also included demonstrating the structural and hydraulic design of a hydraulic jump stilling basins over a rough bed. [ABSTRACT FROM AUTHOR]

This investigation compared the spatial ecology and population dynamics of brown trout Salmo trutta L. between reservoirs with (impact; Langsett Reservoir) and without (control; Grimwith Reservoir) barriers to fish movements into headwater tributaries, and the effectiveness of a fish pass intended to remediate connectivity. Passive integrated transponder (PIT) telemetry revealed that fish that emigrated from Langsett and Grimwith tributaries were 1–3 and 0–2 years old, respectively, and predominantly did so in spring and autumn‐early winter in both systems. Weirs at Langsett Reservoir appeared to thwart emigration rate (26%) relative to Grimwith Reservoir (85%). Acoustic telemetry (two‐dimensional positions) in the impacted reservoir revealed that the largest home range was in October–December (95% monthly activity space S.D. up to 26.9 ± 6.69 ha in November), activity was influenced by both month and time of day, and fish occupied shallow water depths (relative to reservoir depth), especially at night. Brown trout tagged in Grimwith and Langsett Reservoirs (42.9% and 64.1%, respectively) and fish tagged in the tributaries that emigrated (37.2% and 27.7%, respectively) were detected immigrating into tributaries throughout the year. At both reservoirs, peak immigration for ≥3‐year‐old trout occurred primarily in autumn‐early winter. Overall passage efficiency went from 3% prior to remediation to 14% after and there was no significant increase in fish densities following the construction of the fish pass. Fish were attracted towards and entered the fish pass under a wide range of river levels, but only succeeded in passing upstream during low levels, which are uncommon druing the main migration period. Overall, this investigation significantly furthers our understanding of brown trout spatial ecology and population dynamics in reservoirs and headwater tributaries.   [ABSTRACT FROM AUTHOR]

An increasing presence of instream structures such as weirs, dams, culverts and reservoirs degrades habitats, fragments rivers and blocks fish movements worldwide. Longitudinal river movements are fundamental for many fish species and the most widespread solution to restore longitudinal connectivity is the implementation of different fish passage solutions. Fishway functionality, however, is highly variable. To design a functional fishway, several aspects of the fish's interaction with its environment need to be taken into consideration. Artificial light at night (ALAN) can affect a range of different behaviours in fish, from activity and movement to feeding and predator–prey relationships. In a fish passage setting, fish are exposed to artificial light at night (ALAN) in the form of light pollution, but, sometimes, also as part of the fish passage solution. Although likely highly species specific, the effect of artificial light on fish passage behaviour has been little explored. Here we study the passage behaviour of two small‐sized fish species, European gudgeon (Gobio gobio) and Italian riffle dace (Telestes muticellus), over a scaled deep side notch weir in a hydraulic flume in three different light conditions: daylight, darkness and ALAN. Although both species passed the obstacle at high efficiencies under all light conditions, their passage behaviours were influenced by light, particularly at the higher levels. While ALAN reduced passage success and resulted in delayed passage for gudgeon, riffle dace passed at higher rates under the artificial light compared to night treatment. Both results indicate a risk of negative effects from ALAN on passage performance at real fishways—or movement rates in lit areas of natural streams—for both species. Independent of light conditions, individuals of both species also passed faster after repeated trials, demonstrating learning in a fish passage context. [ABSTRACT FROM AUTHOR]

Macroroughness ramps (e.g. with a rough bed and protruding blocks evenly distributed in staggered rows) are nature-like fishways offering a wide range of flow conditions and are expected to be very efficient tools to reduce the impact of weirs on the free movements of most life-stages of riverine fish species. However, their in situ efficiency has not been evaluated yet. Here, we used Radio Frequency Identification (RFID) telemetry to monitor during two years the displacement of eleven fish species, on such a macroroughness ramp located on a tributary of the Loire River in France. We (1) evaluated the migration rates of tagged fish species, poorly documented so far; (2) quantified macroroughness ramp attraction and efficiency; and (3) assessed the influence of fish species, fish length and environmental conditions (river discharge and temperature) on these efficiency estimates. All the species detected downstream of the weir successfully crossed the ramp, although at varying rates. Depending on the analytical approach (considering the whole study duration or taking into account different fish attempts), the ramp attraction efficiency ranged between 65.5% and 52.9%, the ramp passage efficiency between 81.8% and 77.0% and the overall efficiency between 53.6% and 41.6%. Fish between 70 and 451 mm in total length were detected crossing the ramp, usually within a short time. In comparison with the efficiency results available for other types of fishways, the macroroughness ramp studied here ranks among the most efficient devices for fish movement restoration.

Passive integrated transponder (PIT) radiofrequency (RF) chip tracking has been widely used to monitor the fish migration movement, and then quantify fish passage efficiency. The present study aims to determine the fish passage efficiency and the behavior at the Laokou transportation hub of the Yujiang River. The test site of passage was selected as the total length of 718 m, where the design slope of the pool chamber was 1:60. The upstream and downstream water levels varied from 75.46 to 75.53 m, and 67.00 to 67.07 m, respectively, in the test period. The exit and entrance depths of the fishway were 1.8 and 3.1 m, respectively. The dominant specie of Cirrhinus molitorella was used as the test object. The full length of the test fish ranged from 16.00 to 23.50 cm, with a mean value of (19.05±1.49 cm). Half-duplex (HDX) PIT-tagged RF chip tracking system was constructed with the dorsal muscle implantation of PIT tags in the test fish. The behavior of tagged fish was then characterized in five monitoring sections of the fish passage. A quantitative evaluation of passage efficiency was carried out on the fish passage. The flow velocity and water temperature were measured to determine the dissolved oxygen and pH during monitoring. A total of 1 136 signals were collected from the five antennas. The results showed that the tagged test fish passed through the fish passage for an experienced duration of 648 to 5 359 min with a total passage efficiency of 50.79%. According to the ANOVA, there was no significant difference (P>0.05) in the total length of fish passing in the five sections. In addition, specific patterns were found in the fish behavior; The test fish was more active in the fishway at all times during the day (06:00 to 18:00), while at night (18:00 to 06:00) no detection was recorded for 7 h. Furthermore, 80.95% of the individuals rapidly passed up or swam out of the fishway through the monitoring cross-sections, whereas, 19.05% of the individuals experienced a stopover when passing. Passage speeds varied considerably between the two transects, with the slowest speed (0.75±0.32 m/min) through the first transect. Eight fish showed a downward movement in this test. Therefore, the test fish was the most active from 05:00 to 09:00, while there was basically no detection signal at night, indicating that the test fish was in a resting condition at night. There was a basically reasonable flow rate and the residence time of fish passing through the section at Laokou. The duration of passing fish was more than 10 h, most of which was to swim from release to the first section. The slow flow velocity was the important influencing factor in the downstream section of the fish passage. Subsequent experiments also need to enrich the test fish species and number, in order to supplement the fish passage entrance on the entry efficiency. This finding can provide a strong reference to quantify the fish passage efficiency and behavior in crossing facilities. [ABSTRACT FROM AUTHOR]

Fragmentation of watercourses poses a significant threat to biodiversity, particularly for migratory fish species. Mitigation measures such as fishways, have been increasingly implemented to restore river connectivity and support fish migration. The effects of such restoration efforts are typically tested using telemetry and fisheries methods, which do not fully capture the broader population movements that may have important consequences for population viability. We performed a before‐and‐after control‐impact (BACI) study using genetic tools (SNPs) to investigate the effect of a newly implemented fishway, aiming to enhance upstream spawning migration of brown trout (Salmo trutta Linnaeus) in a reservoir with two headwater tributaries fragmented by man‐made weirs. Another reservoir with two barrier‐free tributaries was also analysed as a control. Our results showed that the isolated brown trout population was spawning in the reservoir before the installation of the fishway, and we found genetic structuring and differentiation between fragmented headwater tributaries before the fishway construction, but not in the control reservoir. Unexpectedly, after the fishway construction we observed signals consistent with increased genetic differentiation between populations of newly recruited juvenile fish in the reservoir tributary and fish in the reservoir. We propose this was caused by newly enabled philopatric behaviour of brown trout to their natal spawning tributary. In contrast, we did not find any genetic changes in the tributary without a fishway or in the barrier‐free reservoir system. Given the scarcity of similar studies, we advocate for an increased use of genetic analyses in BACI studies to monitor and evaluate the effect of efforts to restore habitat connectivity and inform future management strategies. [ABSTRACT FROM AUTHOR]

Denil fishways have been used with varying success to help fish pass impediments to upstream passage such as low head dams or irrigation diversion structures. They have been tested for hydraulic and fish passage performance in laboratory and field settings, usually with only minor modifications to the fishway geometry or dimensions. We tested a reduced (0.6) scale prototype of the standard-sized Denil fishway to determine if the smaller fishway, which requires less water flow, would successfully pass Arctic Grayling (Thymallus arcticus). The scaling factor was informed by analyzing previously published scalable Denil fishway rating equations. A prototype was tested in an open-channel flume using 8 treatments with 3 trials per treatment and 8 fish per trial. Each treatment had a prescribed combination of headwater and tailwater depths. Overall, 93% (178/191) of the fish volitionally entered the fishway and of these 91% (162/178) passed successfully. Entrance and passage were reduced only in treatments with the highest hydraulic slopes and highest water velocities at the downstream end of the fishway (i.e. with high headwater depths and low tailwater depths). The 0.6-scaled Denil fishway is likely a good alternative to standard-sized Denil fishways to enhance upstream mobility of Arctic Grayling in small, water-limited streams. [ABSTRACT FROM AUTHOR]

Southeast Asia’s inland fisheries are under threat from extensive irrigation and hydropower development. Of particular concern is the Mekong River, which is currently home to the world’s most productive inland fishery. To minimise these negative impacts, fish-friendly infrastructure can be incorporated into these barriers to facilitate fish migration or “passage.” However, historically fishways have often been overlooked given cost considerations and a lack of awareness of benefits across irrigation managers and funding bodies. This study aimed to understand fishway implementation decision-making across the Mekong. Findings from 19 interviews showed that funding was central to decision-making and acted as an ability and a trigger, to both positively and negatively influence stakeholders’ motivations for fishway implementation. Masterclasses were viewed as key vehicles for building technical capacity and consent within the region through the creation of networks and social capital between irrigation engineers and fisheries staff, as well as the development of “champions.” [ABSTRACT FROM AUTHOR]

: Here internal structures were added into the curved side wall and vertical seam, in order to improve the fish passage efficiency of fishways. Auxiliary fish passage devices were arranged on the inner wall and bottom plate of the fishway. Six layouts were also combined to explore the effect on the fish upstream behavior using simulation and model testing. The results showed that the success rates of upstream migration were 36.7%, 43.3%, and 73.3%, respectively, for the combinations of barriers in schemes 1, 2, and 3. Because scheme 1 was set as more barriers, the flow velocity in the mainstream decreased rapidly to cause the vortex-like flows, where the fish was unable to identify the upstream direction. There was the a low flow velocity in the downstream half of the mainstream, leading to difficultly ascending. A group of barriers was removed perpendicular to the direction of flow in scheme 2. The mainstream flow was connected from the top to the bottom, indicating the fish upstream migration. The sScheme 3 was equipped with the a central connection and only one group of barriers on the side wall. The highest success rate was achieved for fish upstream migration. The wide distribution of mainstream flow velocity and large flow velocity differentiation were provided more selective areas for fish with the different physical abilities, thus improving the fish upstream migration. There were the hindering and disturbing effects of circular columns on the flow in the tank chamber, indicating the variation in the mainstream flow path and flow velocity distribution. There was the an increase in the mainstream branches with the upstream flow velocity decreased. The test fish was easily fieasily found the correct path. The maximum mainstream flow velocity was greatly contributed to the better better-ascending fish. An optimal number of recirculation zones were was also maintained to ensure the rest for upstream fish. The combinations (schemes 4, 5, and 6) of straight circular columns were introduced in the scheme 3 to further improve the effect of fish upstream migration. The success rates were 56.7%, 73.3%, and 90.0%, respectively, for the upstream migration. The internal disturbance was significant in the area that composed of internal barriers in scheme 4, resulting in a narrower middle mainstream width and lower flow velocity than on both sides. There was the a low flow velocity in the tail of the tank chamber. There was no benefit to inducing fish upstream migration. In scheme 5, the width of the middle mainstream increased, while the flow velocity in on both sides decreased. The lower flow velocity and longer distribution distance in the higher flow velocity area were promoted the fish upstream migration, while reducing the swimming difficulty. There was the a cylindrical diameter with one-half of the inlet width of the tank chamber in scheme 6. The highest success rate was then achieved for the test fish upstream migration. The middle mainstream flow velocity increased in the tank chamber. The mainstream was much clearer to fill with internal barriers. There was the a diffusion from the middle mainstream to both sides. The width of mainstream distribution increased for the fish upstream migration. In the recommended solution, the fish swimming was roughly followed the mainstream upstream, providing the multiple mainstream flow paths for fish. The pass efficiency of fish was improved with the large discrimination of flow velocity, the reasonable attenuation of mainstream flow velocity, and the flow pattern with the fewer backflow zones. [ABSTRACT FROM AUTHOR]

The fishway collecting system has been confined to complex flow patterns, diverse operating conditions, and unclear behavioral responses of Chinese carp fish. In this study, an experimental apparatus was constructed to emulate the main structure of a typical collecting system, according to the prevalent size and operational conditions of several fishways in China. 11 sets of tests were carried out under four working conditions. Two water levels and two outflow patterns were collected to observe the attractive rate, attempted rate, and upstream passage rate of mature crucian carp (Carassius auratus) at different spawning stages. Passive integrated transponder (PIT) telemetry within a generalized model was employed to monitor the fish swimming trajectories in the collecting system. Initially, the flow patterns were measured under the four working conditions. The flow velocity at low levels exceeded the high-water levels. The dispersed outflow exhibited greater continuity than the concentrated outflow through water holes from the supplemental water channel to the collecting canal. The experimental results indicated the attractive rates ranged from 5.24% to 94.44%, 41.46% to 92.59%, and 0 to 77.33%, respectively, at the three entrances. The random forest model demonstrated that five predictor variables (spawning stage, outflow condition, level, flow discharge, momentum, and velocity) were used to explain 60.46% of the density variation in the rates of attraction of crucian carp at the entrances, with the better match between predicted and observed values. Spawning stage and water momentum were ranked the first and the second among all environmental variables. Nonparametric statistical tests indicated that there was a significantly higher attractive rate before spawning than after spawning (P < 0.05). There was no significant difference between the small and medium momentum groups (P > 0.05). But both showed a more significant difference, compared with the large momentum group (P < 0.05). The binary logistic regression model revealed that the attempted rate before spawning was 33.032 times that after spawning, while the dispersed outflow from the water replenishing holes was 4.228 times that of centralized outflow, and the higher water level was 2.484 times that of the low water level. Bivariate correlation analysis showed that the upstream passage rate increased with the attempt rate (P < 0.05). The upstream behavior of fish in the powerhouse collecting systems was primarily driven by ecological needs and also influenced by the outflow flow. Momentum was used to comprehensively reflect both flow velocity and flow rate, thereby serving as the better indicator of the rate of attraction, in terms of water flow. However, the higher momentum cannot always lead to higher rates of attraction and is influenced by the ecological habits of fish and their life history stages. At the connection section from each entrance to the main channel of the fishway, continuous guided water flow greater than the attractive speed should be provided to guide the fish to successfully enter the main structure of the fishway and avoid turning back downstream. These indicators should be comprehensively considered in future designs to predict the upstream strategy of fish. [ABSTRACT FROM AUTHOR]

Context: Rapid human population growth has increased demand for water supply, food security, electricity, and flood mitigation worldwide. To address these challenges, governments have invested heavily in the expansion of water infrastructure. However, there is substantial evidence that globally, this infrastructure impacts aquatic ecosystems and can have a significant impact on the persistence of fish species. Despite being well understood globally, the impacts of dams on fish have been given scant attention in Indonesia. Thus, considerations for fish are rarely included in river development planning frameworks. Methods: To document the impact of riverine barriers on Indonesian freshwater fish, we surveyed multiple sites, using three different kinds of gear (gillnets, castnets, and bait traps), upstream and downstream of Perjaya Dam in the Komering River. Key results: The study revealed 13 of 36 species were found only downstream of the dam and five of 36 species were found only above the dam. There were significant differences in fish community composition between upstream and downstream regions using either fish abundance (Pseudo- F = 4.495, d.f. = 1, P < 0.05), species richness (Pseudo- F = 15.837, d.f. = 1, P < 0.05) or species diversity as the response metrics (Pseudo- F = 8.3256, d.f. = 1, P < 0.05). Conclusions: The local extirpation of many species from upstream areas suggests that the Perjaya Dam hinders fish migration. Implications: Despite containing a fishway, the results indicate that fish are not successfully recolonising upstream reaches. Dams are known to impact fish community structure, however, the impacts of dams on the fish community in Indonesia is understudied. We sampled the fish community upstream and downstream of a dam fitted with a fishway, identifying significant differences in fish community structure. This highlights the need for further research into the operation of the dam, and fishway, to improve fish passage success. [ABSTRACT FROM AUTHOR]

For an efficient restoration of ecological continuity, rock-ramp fishways with protruding blocks and lateral slope can allow to conciliate two opposite objectives: sufficiently low flow velocities in some parts of the ramp for fish passage and a large global discharge for attractiveness. Flows in such ramps with several lateral slopes (from 5% to 18.5%), longitudinal slopes (from 1% to 7%) and discharges were investigated experimentally on a one-fifth scale model and numerically with RANS and LES models, to check up their passability compared to ramps with no lateral slope. Results revealed that the methodology for assessing stage-discharge relationship and maximum velocities is still relevant whatever the lateral slope. However, as the lateral slope increases, so does the lateral deviation of the free surface, as well as the transverse and vertical velocities in the emergent part of the ramp, near the submerged part. This is why it appears preferable to limit the transversal slope to a maximum 12% in rock-ramp fishways with protruding blocks. This recommendation is already much higher than the one applied up to now in France (lower or equal to the longitudinal slope, so mostly lower or equal to 4% to 6%) and will allow to reduce the width and thus the cost of the ramp. Highlights: CFD simulation with LES is pertinent to investigate flow in rock-ramp fishway with a transversal slope and protruding blocks either emergent or submerged. Lateral slope up to 12% do not disturb flow in the part where blocks are emergent, which makes it possible to consider lower build-cost fishway. Design procedure for rock-ramp fishway remains valid with lateral slopes with some precautions. [ABSTRACT FROM AUTHOR]

Hydraulic considerations specific for the design of step-pool nature-like fishways (NLFs) are limited to the body dimensions of the target species. Additional hydraulic criteria for flow depth, maximum values for each of pool depth, velocity, and turbulent kinetic energy in terms of the weir opening width and discharge can help design an optimum step-pool NLF. The present study developed design charts and rating curves based on numerical modeling using the computational fluid dynamics software FLOW-3D® HYDRO. Instantaneous velocity measurements on a 1:4 scaled physical model of a step-pool nature-like fishway designed as per the available design guidelines have been used to validate the numerical model. The hydrodynamics of the fishway with respect to the weir opening ratio b r (0.10, 0.25, 0.45, 0.65, and 1.00) and discharge Q (0.1–1.5 m3/s) was analyzed through numerical simulations on a prototype scale. The simulation results showed that the maximum flow velocity and the averaged velocity over the crest at b r = 0.10 and 0.25 are considerably lower than at b r > 0.25. The maximum turbulent kinetic energy and energy dissipation factors for the tested range of discharges were within recommended limits for b r = 0.10 and 0.25. The present study outcome in terms of the design charts and rating curves that illustrate the relationship between different variables can be used for an optimum design and ease in field implementation. In addition, the bed structure of the step-pool NLF presented in this study can be used to recreate full-scale or pilot models. [ABSTRACT FROM AUTHOR]

Globally, fishways perform better when the target fish species are salmonids rather than non‐salmonids. In the past few decades, engineers and dam managers have attempted to identify an ideal fishway type that can fit all migratory orders. To determine a general rule for selecting fishway types, we classified all fish orders into two groups (salmonids and non‐salmonids) and analyzed the effect of different fishway types (i.e., nature‐like [NL], vertical slot [VS], pool and weir [PW], and denil [DL]) on upstream migration for both groups by conducting a meta‐analysis based on data from 64 studies of 76 fishways. The fishway performance was presented in terms of attraction efficiency (AE) and passage efficiency (PE). The results of a random‐effects model, including 257 and 299 estimates of AE and PE, respectively, showed fishway types only had a significant effect on AE for non‐salmonids. Technical fishways had a higher AE than NL fishways for salmonids, but were not applicable to non‐salmonids. The passage results of four fishway types indicated that the PW fishways exhibited the best performance for salmonids, but the poorest performance for non‐salmonids. Only DL fishways had a PE of over 50% for non‐salmonids, whereas all fishway types had that of over 60% for salmonids. Variations in the slope and length of VS fishways could significantly affect PE for both groups, however, the phenomenon for salmonids disappeared when merging all fishway types. Elevation changes had a significant effect only on the condition that salmonids passed through VS fishways. The results of this study play an important role in designing appropriate fishway types for different downstream fish fauna and can be better generalized by complementing quantitative evaluation studies of various fishways as much as possible. [ABSTRACT FROM AUTHOR]

Fish passages are constructed to facilitate movement around barriers, but few are quantitatively evaluated for non-salmonids. We quantified the efficiency of a selective, nature-like fish passage for three native fishes, Colorado pikeminnow (Ptychocheilus lucius), flannelmouth sucker (Catostomus latipinnis), and razorback sucker (Xyrauchen texanus), in the San Juan River, NM, USA, by estimating the probabilities of completing three navigational phases and associated delay times. We compared passage efficiency in years when fish were captured in a trap and manually moved upstream to years when the trap was removed in the spring. All species were less efficient at navigating the attraction and exit phases compared with the ascent phase. Operating the passage without the trap generally increased passage success and shortened delay times. The mean probability of passage and delay time among species when the trap was removed ranged from 34%–55% and 5–21 days, respectively. Our results suggest species- and phase-specific variation in passage efficiency and highlight the need for evaluations to aid future passage design and operation for a greater diversity of fish. [ABSTRACT FROM AUTHOR]

The opposite side vertical joint fishway has the characteristics of better adaptation to water level changes, obvious energy dissipation effect and better flow pattern of water. According to the design guidelines, the fish passage in the study area is designed in body shape. In this paper, the effect of different vertical slit positions on the flow structure of the chamber is investigated by numerical simulation, including the hydraulic characteristics of the main flow area, the hydraulic characteristics of the return flow area and the flow velocity distribution of the vertical slit position, and the vertical slit position of the fish passage suitable for the fish in the study area is analyzed. The simulation results show that: the vertical slit position has almost no effect on the maximum flow velocity in the pool chamber of the opposite side vertical slit, and has less effect on the change of the maximum flow velocity along the main flow area. As the center of the vertical slit gradually approaches the center of the pool chamber, the decay of the maximum flow velocity along the main flow area takes the lead in gradually becoming larger and then tends to saturate. Most of the flow velocity in the return area of the upper left part of the main flow area gradually decreases and then increases, and most of the flow velocity in the return area of the lower right part gradually increases. The area ratio of the two sides of the reflux zone gradually decreases. The vertical slit position on the pool room mainstream area flow pattern and the flow velocity distribution of the return area has a significant impact, when 0.23≤l/B≤0.40, the pool room flow pattern is the best; when l/B≥0.37, the mainstream area along the maximum flow decay rate tends to saturate, when 0.37≤l/B≤0.40, the maximum turbulent kinetic energy in the pool room at l/B =0.40 minimum, and the area of the return area on the left and right sides. Therefore, when l/B=0.40, the migratory effect of semi-migratory fish in the study area can be significantly improved. The maximum variation of turbulent energy in the pool is between 0.074 and 0.116 m²/s² when the vertical slit is located at 0.13-0.50 of the width of the pool chamber from the side wall, and the flow pattern in the pool is the best when the vertical slit is located at 0.23-0.40 of the width of the pool chamber, which can significantly improve the migratory effect of semimigratory fish in the study area. The results of the study clarify the influence of the center position of the vertical joints on the water flow structure of the pool chamber and provide a reference for the subsequent design and research work of other related fish passage projects. [ABSTRACT FROM AUTHOR]

The Tesla valve has a special structural form that can guide the flow entering from the reverse port into two sets of straight/curved channels, and dissipate energy through friction and collision at the end of the guide column, greatly weakening the flow velocity in the pool. This unique flow characteristic is very suitable for designing fishways. However, direct applying the original structure of Tesla valves as a fishway has been proven to have significant limitations. The original structure of the Tesla valve fishway is optimized in this paper. By adjusting the aspect ratio of the straight/curved channel in the fishway pool, hollowing out the guide column, and increasing the length of the opening end, a new Tesla valve fishway with relatively independent energy dissipation channels and fish upstream channels has been obtained. The hydraulic characteristics parameters of the optimized Tesla valve fishway are compared with the original structure using numerical simulation, with a focus on analyzing the flow velocity variation, flow field, and turbulent energy distribution of the new Tesla valve fishway. The results show that the new Tesla valve fishway has significant advantages compared to the original structure. While maintaining the same energy dissipation efficiency, it effectively improves the flow pattern in the pool, and the overall flow velocity and turbulent kinetic energy are smaller than the original structure. The new structure significantly increases the proportion of rest areas. When the pool bottom slope gradient from 1% to 3%, the proportion of rest areas in the original Tesla valve fishway is 8.5% to 1.2%, while the proportion of rest areas in the new Tesla valve fishway is 44.7% to 25.8%, increasing the possibility of successful fish upstream migration. The flow velocity and turbulent kinetic energy of the new structure increase with the increase of the bottom slope gradient, but the flow velocity remains low in the fish upstream channels, while the high flow velocity mainly occurs in the energy dissipation passage. The maximum flow rate increase rate in the energy dissipation channel of the first two stages of the pool is relatively high, while after the third stage of the pool, the increase rate tends to slow down. The overall turbulent kinetic energy in the fish upstream channels is relatively low. When the bottom slope gradient is less than 2.5%, the upstream conditions and economy of the fishway are better. [ABSTRACT FROM AUTHOR]

Purpose: to assess the state and operating conditions of the fish passage channels of the Ust-Manych waterworks on the river Western Manych. Materials and methods. The factual basis for assessing the state and operating conditions of the Ust-Manych fish passage channels was the materials of the author’s survey and field studies performed at the given facility in 2022. The studies were carried out according to generally accepted methods for conducting hydrometric measurements of flow rate parameters and geometric dimensions of channels and network (“canal”) hydraulic structures. Results and discussion. The survey data of structures and elements of two fish passage and spawning channels operating as part of the Ust-Manych waterworks, designated for passing semi-anadromous fish from its tail race to the head race - from the mouth of the river Western Manych to the Ust-Manych flood plain which is a potentially highly productive spawning ground for phytophils (bream, pike perch, carp and ram). The channel hydrometric parameters are given, a description of the structures included in their composition, ensuring the functioning of structures and structural elements or influencing it is given. The characteristics of the water flow on the structures and along the canal tract, as well as on the site of the conjugation of the canal mouth with the river are given. Estimated qualitative and quantitative indicators of the conditions for fish channel functioning are given. Conclusions. The survey data of the current state of structures and structural elements of two fish passage channels arranged around the Ust-Manych waterworks retaining structures were obtained. The hydrometric (flow-rate and geometric) channel parameters are given, and an assessment of the quality of their operating conditions on spawning-migratory fish passage from the river Western Manych to the spawning grounds located in the channel basin of the Ust-Manych waterworks is made.

With the development of hydraulic structures, rivers are becoming fragmented, and their connectivity is greatly affected. Important migratory routes through which fish complete their life processes are hindered. In severe cases, it may lead to the extinction of fish species. As facilities commonly used to assist fish upstreaming, fishways are significant for environmental remediation and have received attention from different scholars. This article proposed a new type of fishway, inspired by Tesla valves with obstructing reverse flow characteristics and classic fishway structures. Due to its characteristic of introducing a water-blocking island structure, it was denominated as an island-style fishway. This work studied an island fishway through a combination of physical models and numerical simulations. The results show that this fishway could achieve various flow patterns suitable for fish migration, and the flow rate control was stable. This study also explored the impact of island spacing arrangement on the turbulent structure of the pool chamber. It was found that when the island distance is set at 1.5d, indicators such as flow velocity and turbulent kinetic energy could achieve significant control effects. However, inappropriate d values might cause adverse effects. This research could provide reference ideas for the design of new fishways. [ABSTRACT FROM AUTHOR]

• Our study introduces a coupled machine-learning-individual-based model (ML-IBM) for migration dynamic simulation. • Multiple hydraulic and inertia indicators were considered. • The stochastic nature of fish movement was considered during the modeling process. • Our model outperformed traditional methods in migration dynamic simulation. • Flow velocity and initial swimming speed play a crucial role in migration dynamic modeling. 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. [ABSTRACT FROM AUTHOR]

In this study, radio telemetry was used to examine the upstream spawning migration behaviour of anadromous brown trout (sea trout), Salmo trutta L., in a boreal river system, the River Isojoki, western Finland. The aim was to study the movement activity and migration characteristics of trout during the upstream spawning migration, as well as to locate the important spawning habitats and study the spawning characteristics. Furthermore, the authors analysed how flow conditions and a hydropower dam, with adjacent fishways, affected the upstream spawning migration. Tagged trout spawned in both the main stem and four tributaries, with spawning taking place from early October to November. The movement activity of radio‐tagged trout was influenced by a hydropower dam (Perus dam), with spring migrators spending prolonged periods at the dam area, postponing the migration upstream. Flow conditions affected the total time spent at the dam area, as well as the movement activity in the free‐flowing sections above the dam, with increasing flow stimulating activity. In addition, time of river ascent and location of spawning area had a significant effect on the movement activity of tagged trout. These results are further evidence that synergistic effects of flow and migratory obstacles can negatively influence migrations of anadromous fish, regardless of constructed fishways. The management of flow regimes and the efficiency of fishways are vital, as climate change will likely influence the flow and increase the water temperature of boreal river systems, further aggravating issues caused by obstacles. [ABSTRACT FROM AUTHOR]

Fishway is one of the common measures to maintain the continuity of rivers and protect fish resources in the world. Among them, the hydraulic characteristics of the early fishway cannot match the swimming ability and habits of the domestic fish, particularly in the early stage of construction. Fortunately, the internal structure can be optimized to improve the efficiency of fishways operation in recent years. However, the complicated physical experiment depends greatly on seasonal, temperature, light, and external factors. Additionally, the test cost is ever increasing in a large amount of fish and feeding. Therefore, it is a high demand to predict the fish migration routes in the field of fish conservation using mathematical models. Taking Schizothorax prenanti as the research object, this study aims to simulate fish migration in the vertical slot fishway. The original data set was divided using upstream data monitored in the previous test, according to the swimming characteristics of Schizothorax prenanti. Random Forest (RF), XGBoost, K-Nearest Neighbors (KNN), and Gradient Boosting Decision Tree (GBDT) were used to establish the multiple Behavior classification model (BCM), and Swimming speed regression model (SSRM). According to the evaluation indexes of the classification and regression model, the optimal model was selected to establish the mapping relationship between the fish behaviors and hydraulic indexes using the Eulerian-Lagrangian-agent method (ELAM) framework, and then the fish migration model was constructed. The improved model also considered the influence of velocity (magnitude, vector, and velocity gradient) and inertia factors on the movement of fish. Specifically, the perception area of the fish body was represented by a two-dimensional circular plane with the inductive distance as the radius, particularly with the center of the fish body as the origin. Finally, the simulated and the observed track were compared to verify the reliability of the fish migration model. The results showed that the RF model performed the best to predict the swimming behavior classification and swimming speed regression. The classification accuracy of swimming behavior was 0.804, the recall rate was 0.794, and the F1 score was 0.798. The R2 values were all greater than 0.75 for the swimming speed regression using the three data sets. The predicted trajectories of the migration model were better agreed with the actual. Most virtual fish successively passed through the mainstream and the right backflow area, indicating better consistency with the actual fish passing experiment. A comparison was made to obtain the characteristic track of the numerical simulation and the actual fish test. Consequently, the fish migration model can be expected to fully reflect the basic behavior characteristics of the target fish, and then to better predict the migration route of Schizothorax prenanti. The finding can also provide a strong reference to evaluate the fishway flow field for the protection measures in the fish industry. [ABSTRACT FROM AUTHOR]

Fishways are used to allow fish to migrate around water infrastructure, whether movements are in the upstream or downstream direction. Hydrodynamic conditions within various fishways, including turbulence levels, are important for successful fish passage. A numerical hydrodynamic study was conducted for V‐weir fishways, which assist species migrating upstream. The variables investigated included, fishway slopes of 4%, 7%, and 10%, relative spacing between weirs of 1.3, 2.6, and 4 (D/L, ratio of distance between weirs to pool width), and weir angles of 22.5°, 40°, and 60°. Turbulence characteristics, including turbulent kinetic energy (TKE), Reynolds shear stress (RSS), turbulent intensity (TI), turbulent dissipation (TD), as well as maximum water velocity, were examined by CFD (computational fluid dynamics) simulation using a re‐normalized group or RNG turbulence model. The CFD was calibrated with flow measurements made in a physical model of the V‐weir fishway in laboratory control experiments. Based on inferences from fish passage literature, the results showed that, in the range of parameters studied, a weir angle of 22.5°, a slope of 10% and relative spacing between weirs of 1.3 and 2.6 were assessed as offering the best potential performance for several species and sizes of fish, while the latter has lower cost as it requires fewer weirs. The V‐weir fishway may be adaptable for smaller fish. [ABSTRACT FROM AUTHOR]

In 1969, a dam was constructed on the Vistula River, the longest in the Baltic drainage basin, 276 km from its estuary, which resulted in the collapse of migratory fish populations throughout the drainage basin. The existing, ineffective fishway was rebuilt in 2014. Monitoring at the new fishway indicated that 24 fish species used it, and over a period of five years the number of individuals fluctuated from nearly 4,000 to over 23,000. Radio frequency identification (RFID) technology was used to investigate 12 fish species, mostly vimba and bream, passing through the fishway. Fish caught in a trap in the upper part of the fishway were tagged with PITs and then released below the dam. Returning fish were recorded by four loop antennas. Of the 877 fish that were tagged, 13% returned to the fishway mostly on the first and fourth days following release. Of the fish that returned, 30% turned back while passing through the fishway: 30% vimba and 52% bream. The transit time of vimba and bream did not depend on fish size or the time after which they returned. Overall, estimated fishway efficiency based on the migration of the tagged fish was high. [ABSTRACT FROM AUTHOR]

A vertical slot fishway (VSF) is among the most effective and commonly used fishway structures to enable fish to pass through artificial barriers such as dams and weirs in the river. Nevertheless, such structures need further improvements in providing better swimming conditions for fish inside the pool and enhancing attraction at the entrance. Therefore, the main objective of this study was to investigate the influence of slope and whether integrating some cylinder structures inside the fishway could enhance further attraction and provide better swimming conditions for fish. This study consists of several numerical simulations, first considering the fishway without cylinder elements while testing three different slopes under two different discharges. Then, the same numerical simulations were conducted, considering cylinder elements of different diameters and arrangements inside the fishway. The numerical model was validated by comparing computed velocities with those measured experimentally from the literature. The results show that the maximum velocity and turbulent kinetic energy (TKE) in the main jet increase as the discharge increases on the same slope. The flow velocity and TKE decrease in the areas inside the pool and between the two baffles. Introducing cylinder elements inside the fishway reduces the principal flow' s maximum velocity. Also, inside the pool, low-velocity regions were expanding. A comparison between the design with a cylinder and the simple VSF indicates that the presence of a cylinder reduced the maximum velocities for the smallest and highest slopes by 6.21% and 9.86% on average, respectively. However, in terms of TKE, cylinders inside the fishway could provide better performance than simple VSF, mainly for low-flow conditions. Finally, this study's solution-oriented findings provide insights that could help design cost-effective fishways by improving particularly fish attraction to the fishway. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel investigation of hydrology's impact on fishway effectiveness. • Combined lab and real-world independent field tests. • Focused on Iberian barbel ascent movements, applicable to other species. • Uncovered vital factors in fish migration and fishway assessment. • Suggested design, retrofitting, and management updates for climate resilience. River systems are highly dynamic, affecting all associated structures and their derived uses. This is particularly relevant for applications such as hydropower production and other water abstractions. This dynamic nature also extends to mitigation measures like fishways, which are vital for reducing the impact of river fragmentation on fish populations. Fishways must be designed to balance biological and hydraulic fish requirements, needing adaptability to varying boundary conditions. This study examines the effect of hydrological variability on fish passage through fishways, particularly for the Iberian barbel (Luciobarbus bocagei). We hypothesized that hydrological scenarios can significantly affect upstream fish passage. To test this, we conducted laboratory and field studies, assessing fish movement under different boundary conditions. We compared passage rates, time metrics, and their correlations with the evolution of fishway hydraulics, and employed survival analysis to determine biometric limits. Our findings show that hydrological changes markedly influenced fish passage rates and timings, producing fish size selection and highlighting the impact of factors such as maximum velocity and power dissipation in the studied metrics. These insights underline the necessity of incorporating hydrological variability into fishway design and management, enhancing their effectiveness for fish conservation in river ecosystems, particularly under growing climatic uncertainties. This research underscores and discusses the need for comprehensive, long-term hydrodynamic studies in fishway assessment and design, advocating for adaptive management strategies to accommodate environmental changes. [ABSTRACT FROM AUTHOR]

Cylindrical Bristle Clusters (CBCs) provide a multi-species fish passage solution at sloped weirs. Configurations trialled to date (min. diagonal spacing between CBCs up to 0.17 m) were designed to facilitate passage of relatively small (e.g. < 30 cm) potamodromous species and may hamper the movements of larger bodied (e.g. > 40 cm) fishes, such as adult anadromous salmonids. Therefore, in this study, the hydraulic conditions created by an array of large diameter (0.13 m) CBCs positioned farther apart than in previous studies (min. diagonal spacing 0.29 m) was assessed to determine whether conditions would be suitable for facilitating the passage of small-bodied fish while also providing sufficient space for larger individuals to manoeuvre. Two experiments were conducted in an open channel flume. Experiment 1 quantified the hydraulic conditions created by a model Crump weir when unmodified and with CBCs installed in supercritical flow (Fr 1.23–3.01) on the 1:5 downstream sloping face under a low (0.08 m3 s−1) and high (0.23 m3 s−1) discharge. Patches of low water velocity were created in the wake of the CBCs, and the median (time and space averaged) velocity was reduced under both low (30.1%) and high (22.3%) discharge. Based on estimated burst swimming speeds of two common European species, the roach (Rutilus rutilus) and brown trout (Salmo trutta) (0.16 m long, swimming at 15.1 °C), this reduction in velocity would facilitate upstream passage. Experiment 2 documented the vertical velocity profile and shear stress characteristics (a measure of turbulence) within the CBC array. Unlike in Experiment 1, the CBCs were installed on the flat base of the flume and under subcritical flow (Fr = 0.31) to generate sufficient water depth. The velocity was reduced (up to 22.5%) at depths that did not exceed (> 2 cm above) the height of the bristles. Above these depths, velocity was (up to 14.6%) higher compared to open channel conditions upstream of the CBC array and a vertical shear layer was evident. As the main hydraulic benefits of CBCs occur at depths that do not exceed the bristles, their height should be tailored to site specific conditions (e.g. size of target fish species and/or depth of water at infrastructure). Field-based research is needed to determine velocity reduction at longer weirs and under a wider range of flows than can be tested under flume conditions. How the hydraulic characteristics of submerged CBCs differ from those described here with those that occur in the field when installed on a steep sloping weir under supercritical flow should be further investigated. • A large diameter CBC fish pass reduced water velocity at a model Crump weir. • The velocity reduction would likely ease passage for common European fishes • Under low Q CBCs did not increase depth; a depth barrier may remain for fish. • When submerged, hydraulic benefits for fish occur within the height of the bristles. • Bristle height should be tailored to site specific conditions to maximise benefits. [ABSTRACT FROM AUTHOR]

The purpose of this study was to allow fish to move upstream past barriers or difficult sections of passage, even on steep stream-type fishways. Therefore, the authors devised a roughness arrangement to raise the water depth in the fishway and reduce its flow velocity. Roughness was used as a group in the arrangement so as to expect afflux effects. Water depth was raised and the flow velocity was reduced around the roughness groups, which allowed fish to hold position and move upstream. Although rapid flow was locally formed in some spots in the fishway, its area was small, enabling the fish to move upstream sufficiently. The experimental results obtained in this study will be applied as a removable stream-type fishway to small channels, head constructions, and so on where fishways cannot be installed due to management. [ABSTRACT FROM AUTHOR]

Simple Summary: Hydraulic 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. [ABSTRACT FROM AUTHOR]

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Physical and 3D numerical hydrodynamic flow models and an agent-based model are developed with the principal objective of analysing fish behaviour in two vertical slot fishway configurations. Fish energy consumption due to swimming represents a crucial criterion for selecting an appropriate fishway configuration. The modelled fish detects ambient flow conditions, makes decisions based on its sensing and cognitive abilities, adapts to the changes in its environment, and moves toward the regions of less turbulent kinetic energy. The results show that fishways with longer pools enable passage of fish at a lower energy consumption.

Irrigation infrastructure expansion threatens the diversity of freshwater fish worldwide. Irrigation infrastructure creates migration barriers which can block access to important nursery, feeding and spawning habitat. Lao PDR is a landlocked country situated within the Lower Mekong River Basin where there is a substantial dependency on rice and fish for food, income and livelihoods. The country is experiencing an unprecedented boom in irrigation infrastructure investment, with modernisation programs being implemented in every province. Despite significant investment in infrastructure upgrades, and the potential impact on freshwater fish, little consideration has been given to fish passage solutions. In 2008, we commenced a fish passage program in Lao PDR. The intent of this case study is to outline the pivotal elements of the program of knowledge development and transfer, in the context of river connectivity and fisheries management in Lao PDR. We also highlight challenges in international research in development and lessons learned.

Fishways are being provided more regularly than ever before and new designs are needed to provide passage for whole fish communities. Despite recent progress, fishways have frequently performed poorly, especially for small-bodied fish (i.e. 10–100 mm long), which can form large aggregations below stream barriers. This was the genesis for the development of the cone fishway design, a new style of technical fishway which consists of a series of pre-fabricated cone-shaped concrete baffles installed laterally within a concrete channel. The cone design arose from the need to install rock ramp fishways at remote sites where rock was unavailable and where maintenance would be infrequent. The objective of the present study was to evaluate the suitability of the new cone fishway design to provide passage for small-bodied diadromous species (i.e.

This study aims to describe pre-reproductive movements of Luciobarbus bocagei and Pseudochondrostoma duriense in a regulated canyon-stretch of the Tormes River (Spain), with high environmental variability, semipermeable barriers, and fishway retrofitting actions. The main objectives were to identify peak migration dates and environmental drivers, test ensemble-learning techniques to model fish migration and propose adaptive management measures. To achieve this, fish movements were 5-year monitored in a stepped fishway and Survival Analysis and Random Forest techniques were used for data analysis and modelling. Results showed that migration occurred in May–July, a wider period than the one previously reported in the literature. Movements were triggered by the increase in water temperature and photoperiod, and were strongly affected by the hydraulic river scenario (water levels and discharge) at the semipermeable barriers. Random Forest was able to include the effect of each barrier and predict accurately timing and number of migrants, classifying and ranking the importance of variables. Moreover, developed models allowed to assess fishway retrofitting actions and to predict positive effects in fish number under new, scheduled and variable environmental flow scenarios. Long-term monitoring together with ensemble-learning methods can allow the definition of cost-effective adaptive management strategies to ensure endemic fish conservation. [ABSTRACT FROM AUTHOR]

In this study, a hydraulic analysis technique is presented for evaluating the efficiency of a pool-weir type fishway. The River-2D model with the fish physical habitat module was used for the analysis of the attraction efficiency, and the weighted usable area proposed as an index of the efficiency. For the analysis of passage efficiency, the three-dimensional model, FLOW-3D, was used as an evaluating tool to describe the fluid behavior on a hydraulic structure with a free surface. The ice-harbor type fishway at Dalseong weir in the Nakdong River of Korea was selected as a test-site, and the efficiency was estimated using the hydraulic analysis. The results of River-2D analysis showed that the location of the fishway near the right bank now was not appropriate for attracting the target fish to the fishway due to the deep water depth. The 3D analysis results presented that the flow velocity field inside the fishway showed a similar plunging flow in each pool, but various flow patterns appeared locally. [ABSTRACT FROM AUTHOR]

Fish passage structures have been constructed to facilitate fish movement past barriers, though the effectiveness of passage structures is highly variable. Designing fish passage structures that consider the behavioural preferences of fish under different environmental conditions (e.g., light colour, substrate type) has the potential to improve fish passage success. Similarly, whether a fish encounters a passage facility alone or in a group may influence fish behaviour. In this case, we assessed the preference of different group sizes (n = 1, 6 and 12, respectively) of David's Schizothoracin Schizothorax davidi under four different light‐emitting diode colours and eight different substrate types in the aquaria of the Houziyan Reproduction Station. We found that singletons preferred to visit the white light, cement and fine pebble, while the fish in groups preferred to visit the blue light, fine pebble and cobble. In addition, the total percentage of mobility frequency (18.3 ± 1.8%), movement velocity (20.4 ± 15.9 cm/s) and distance moved (15.8 ± 1.8 m) of singletons in blue light were much lower than that in the others. The movement velocity (3.3 ± 0.6 cm/s) of singletons on cobble was less, but the percentage of total mobility time (162.9 ± 16.0%) and distance moved (153.4 ± 19.6 m) on the cobble were much greater. Our research yielded novel insights for improving passage efficiency for this species. Findings from this study suggest there should be greater consideration of light colour and substrate type when designing fish passage facilities. Because fish almost always experience dynamic hydraulic conditions near and in fishways, additional research is needed to understand the generality of these findings in systems under lotic characteristics. [ABSTRACT FROM AUTHOR]