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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]

The migration corridors in regulated rivers lead downstream fish migrants, particularly juveniles to pass through water infrastructure. Accelerating flow, experienced by fish, might trigger avoidance behaviour and then influence the downstream migration efficacy. It is essential to understand the causes of avoidance behaviour exhibited by downstream migratory fish in accelerating flow. In this study, the effect of three different accelerating flows on the downstream migration behaviour of Schizopygopsis younghusbandi (S.Y) was investigated using a constriction wedge in a circulating flume. The results showed that some fish (30%, 23%, and 39% under low, medium, and high flow conditions, respectively) repeatedly attempted to burst upstream with positive rheotaxis prior to successful passage downstream. Under the low‐, medium‐, and high‐accelerating levels, the average fish swimming speeds were 89.19, 91.28, and 111.94 cm/s, respectively; these values were close to the critical swimming speed (110.42 cm/s) of the target fish. The water velocities at the fish avoidance points were centrally distributed at approximately 73.03 cm/s. Regarding turbulence, the results exhibited that the S.Y generally responded to a discrete range of <50 cm2/s2 of turbulent kinetic energy and < 2 N/m2 of the horizontal component of the Reynolds shear stress (RSSxy). Also, the fish that exhibited avoidance behaviour were not centrally distributed in the lateral and longitudinal velocity locations, where there was an abrupt change in the gradient. This study highlighted the impact of accelerating flow on the downstream fish migration behaviour of a cyprinid. Furthermore, this study quantified the hydraulic factors that triggered this avoidance. Thus, it provided experimental support for optimizing the design of the hydraulic factors for downstream fishways. [ABSTRACT FROM AUTHOR]

Vertical slot fishways (VSFs) are the most efficient and least selective typology of technical fish passage, due to their ability to remain effective even when significant upstream and/or downstream water level fluctuations occur. Fishway construction costs can be reduced by increasing its bed slope, but this affects the flow field inside the pools, with higher head drops between the basins, as well as turbulence levels and flow velocities, which may affect fish passage. In light of this, a VSF was investigated by 3D numerical simulations to identify the possible effects of the bed slope (using values from 1.67% to 10%) on the flow field and subsequent implications for fish passage. A particular focus was devoted to cyprinind species, but the results can be extended to other species of similar swimming abilities and, therefore, be applicable to multispecies rivers. Flow velocity and turbulence values such as turbulent kinetic energy and Reynolds stresses were analysed from a fish passage perspective in relation to threshold values derived from previous studies. Pool areas where turbulence values are compatible with fish ability and behaviour were quantified. Maps of the location of fish‐friendly zones in the VSF pools were produced and can constitute a reference for practical applications in fishway design. The flow field generated with bed slopes lower than 6.67% is more compatible with fish swimming capabilities, because it exhibits a predominantly 2D behaviour and more suitable hydraulic conditions, whereas at higher slopes, turbulence levels in the pools increase. [ABSTRACT FROM AUTHOR]

Highlights • Sturgeon population declines are largely due to human activities, especially the numerous dams with no effective fishways. • Knowledge about swimming performance in complex hydraulic conditions is needed to design effectively two-way fishways. • Ecohydraulic research on fishways are restricted by biological and methodological factors, especially for large species. • Swimming performance and fatigue, and single vs multiple variable models are needed to improve sturgeon fishways. Abstract The rapid decline in sturgeon populations is largely a result of human activities, especially the proliferation of hydraulic structures and lack of fish passage systems effective for sturgeon. This review highlights: (1) the importance of sturgeon conservation; (2) the need for data on swimming performance, including capability, metabolism and kinematics; (3) the relevance and limitations of swimming performance data in designing fish passage systems; (4) the need for experiments to develop sturgeon fishways that better reflect natural conditions. A proper understanding of swimming performance is crucial for designing effective fish passage systems. Although swimming performance and fish passage have been investigated for decades, knowledge and results have been limited by biological, methodological and analytical restrictions. To continue advancing passage effectiveness, continued research is necessary on sturgeon swimming performance and its interface with complex fishway hydraulics. [ABSTRACT FROM AUTHOR]

Abstract A dam will be built in the upper reaches of the Mekong River, obstructing fish migration and gene exchange, and a fish lift will be constructed to mitigate these impacts. Target species for the lift were selected based on five criteria: (1) passage demand, (2) passage utility, (3, 4) protection worthiness (protection class and economic value) and (5) fish resource status. Swimming performance of target fish species were assessed and the results were used to recommend velocity criteria for the lift. Swimming performance was assessed by measuring induced flow velocity (U ind , the lowest water velocity that induces continuous fish motion against the flow), critical swimming speed (U crit) and burst speed (U burst). The relationship of swimming performance to body length was also investigated. The research led to three primary findings: (1) The absolute U ind and U crit (m/s) were positively correlated with body length, whereas the relationship between the absolute U burst (m/s) and body length were inconsistent. (2) The flow that was 90% effective in reaching the desired endpoint (EF90) was used to set fish lift design criteria for flow velocity. The EF90 value for U ind (90% induction rate) was 0.17 m/s and the values for U crit and U burst (90% success rates), were 0.62 m/s and 0.87 m/s. (3) Recommended velocity criteria for the fish lift are as follows: entrance velocity, 0.37–0.87 m/s (0.6 U crit-EF90 – U burst-EF90), with mean velocity 0.50 m/s (0.8 U crit-EF90); passageway velocity, 0.17–0.50 m/s (U ind-EF90 –0.8 U crit-EF90), with mean velocity 0.37 m/s (0.6 U crit-EF90); holding chamber velocity, 0.17–0.37 m/s (U ind-EF90 –0.6 U crit-EF90), with mean velocity 0.27 m/s [(U ind-EF90 + 0.6 U crit-EF90)/2]. The approach developed in this case study has good potential as a general method for selecting target fish species and setting site-specific flow velocity criteria for fish passage design. [ABSTRACT FROM AUTHOR]

Fishways have been developed to restore longitudinal connectivity in rivers. Despite their potential for aiding fish passage, fishways may represent a source of significant energetic expenditure for fish as they are highly turbulent environments. Nonetheless, our understanding of the physiological mechanisms underpinning fishway passage of fish is still limited. We examined swimming behaviour and activity of silver redhorse (Moxostoma anisurum) during its upriver spawning migration in a vertical slot fishway. We used an accelerometer-derived instantaneous activity metric (overall dynamic body acceleration) to estimate location-specific swimming activity. Silver redhorse demonstrated progressive increases in activity during upstream fishway passage. Moreover, location-specific passage duration decreased with an increasing number of passage attempts. Turning basins and the most upstream basin were found to delay fish passage. No relationship was found between basin-specific passage duration and activity and the respective values from previous basins. The results demonstrate that successful fishway passage requires periods of high activity. The resultant energetic expenditure may affect fitness, foraging behaviour and increase susceptibility to predation, compromising population sustainability. This study highlights the need to understand the physiological mechanisms underpinning fishway passage to improve future designs and interpretation of biological evaluations. [ABSTRACT FROM AUTHOR]

The disruption of river connectivity through the construction of barriers used for hydropower development and water control purposes can severely damage river ecosystems, reduce the quality of fish habitat, and prevent the upstream migration of fishes. Fishways function as a means of passage around barriers for fish migrating both upstream and downstream. In 2009, the CanFishPass project was initiated in a partnership with Fisheries and Oceans Canada and Carleton University to create a searchable database containing specific information on fishways in Canada built to enable upstream passage. In this paper we evaluate the information gathered in the CanFishPass database to identify trends concerning fishways and fish passage in Canada, yielding, we believe, the first national-scale trend analysis related to fishways anywhere in the world. Although CanFishPass may not include all fishways in Canada, our analysis identified 211 which are primarily located along the coasts and along major rivers and water bodies such as the Great Lakes. British Columbia has the largest number of fishways in Canada (62) and Prince Edward Island has the fewest (2). The most popular type of fishway is the pool and weir fishway (85), followed by vertical slot (37) and Denil type fishways (23). Fishway construction has proceeded at a steady rate since the 1970's, although there has been an increase in the number of nature-like fishways since the year 2000. The majority of fishways are installed to pass salmonids in Canada, although some fishways on warmwater systems pass large components of the fish community. Only 9 % of the fishways in Canada have been studied using methods that enable proper evaluation of biological effectiveness. We recommend that evaluations be carried out at new and existing fishways and that these evaluations enable the determination of attraction and passage efficiency. Additionally, we recommend that future fishway projects and evaluations in Canada be advised to submit details of their work to CanFishPass so that knowledge of these fishways is centralized. Similar efforts on a global scale could lead to opportunities to identify patterns in fishway design and biological effectiveness that would ultimately inform decision making and improve connectivity where deemed necessary. [ABSTRACT FROM AUTHOR]

Dams and weirs strongly affect or interrupt the longitudinal connectivity of rivers, by limiting the movements of several fish species while altering and fragmenting habitats. Fishways, especially pool-type fishways, are used to diminish this impact by enabling fish to negotiate barriers. The aim of this work is to study the behaviour of a small-sized resident cyprinid fish, the Iberian chub- Squalius pyrenaicus (Günther, 1868)-within a prototype of a pool-type fishway, equipped with both surface notches and bottom orifices, and experiencing two different flow regimes, plunging and streaming. Results show that the fish tended to be more successful in their upstream movements under streaming flow and that, for this regime, the surface notch was the preferred route for upstream movements. Flow velocity patterns corroborated the results, showing that the plunging flow regime may have driven fish downstream, while the streaming flow regime may have attracted fish upstream. The plunging flow also prevented access of this surface-oriented species to the surface notch, effectively reducing the area available for transport. Thus, the streaming flow regime can be a sound option for this and other small-sized species, as it enhances fish movements through the fishway. [ABSTRACT FROM AUTHOR]

Abstract: For centuries, humankind has constructed dams on rivers to control flooding, provide for irrigation and utilize potential energy for power, but generally dams had no or little provision for fish passage. Thus, they often blocked or impeded fish migrations. Empirical observations and “trial and error” approaches that characterized historical efforts to develop passage systems for upstream migrating fish often did not work. The first concerted efforts to develop scientifically based fishways for upstream migrant fish began in the early 1900s in Europe with field and laboratory testing of different fishway designs. These were followed by extensive efforts beginning in the 1940s in North America. Scientifically based testing of configurations for fishways for downstream migrant fish began in the 1950s. Nearly all early efforts were directed at salmonid species, with smaller efforts on shad. Recent species at risk legislation in the U.S.A., Canada, and Europe places renewed emphasis on fish passage for all migratory species, and efforts have also begun to develop successful passage strategies for migratory species in other countries worldwide. This has led to renewed efforts to develop effective passage systems and to try creative solutions using natural materials in addition to concrete or metal used in standard technical fishways. Regardless of the type of structures built, history has shown that the most effective means to develop successful installations has occurred when engineers and biologists worked together systematically to design passage structures based on the ability and willingness of fish to seek and accept the hydraulic conditions presented to them. [Copyright &y& Elsevier]

Abstract: Turbulence is a complex phenomenon which commonly occurs in river and fishway flows. It is a difficult subject to study, especially biologically, yet turbulence may affect fish movements and fish passage efficiency. Studies on quantifying fish responses to turbulence, particularly within fishways, are lacking. This study investigated the swimming behaviour of 140 adult Iberian barbel (Luciobarbus bocagei) of two size-classes (small fish: 15≤TL<25cm, large fish: 25

The addition of substrates to small instream obstacles, like low-head ramped weirs, has been considered a useful management solution to retrofit those structures and enhance fish passage. Substrate dimensions and spatial arrangement, together with discharge, and consequently water depths, appear as important factors for the creation of hydrodynamic conditions that may facilitate the successful passage of fish, though related studies are scarce to support decision-making. This study assessed the influence of discharge (Q) and different retrofitting designs (RD) on the upstream passage performance of a potamodromous cyprinid, the Iberian barbel (Luciobarbus bocagei). Different substrates (small boulders, large boulders, cobbles) and spatial arrangements (aligned, offset) were tested. Numerical modelling was performed to characterize the hydrodynamics. Results indicate that Q and RD influenced the upstream negotiation of ramped weirs. Cobbles randomly distributed along the ramp (Nature design) was the most successful configuration, recording the highest number of upstream passages. Low velocities along the ramp, and low turbulence downstream, were registered in this configuration, indicating that the use of natural substrate may help to increase the permeability of ramped weirs to fish movements. The outcomes from this work can help engineers and biologists to design more appropriate passage structures for low-head instream obstacles. [ABSTRACT FROM AUTHOR]

Most fishway studies are conducted during the reproductive period, yet uncertainty remains on whether results may be biased if the same studies were performed outside of the migration season. The present study assessed fish passage performance of a potamodromous cyprinid, the Iberian barbel (Luciobarbus bocagei), in an experimental full-scale vertical slot fishway during spring (reproductive season) and early-autumn (non-reproductive season). Results revealed that no significant differences were detected on passage performance metrics, except for entry efficiency. However, differences between seasons were noted in the plasma lactate concentration (higher in early-autumn), used as a proxy for muscular fatigue after the fishway navigation. This suggests that, for potamodromous cyprinids, the evaluation of passage performance in fishways does not need to be restricted to the reproductive season and can be extended to early-autumn, when movements associated with shifts in home range may occur. The increased effort during the non-reproductive period suggests that adapting the operational regime of fishways, at biologically meaningful seasons in a year, should be assessed by considering the physiological state of the target species. [ABSTRACT FROM AUTHOR]

The objective of this research was to determine the effects of diel cycle and flow velocity on rheotaxis, measure the swimming performance of Perch-barbel (Percocypris pingi , Tchang, 1930) and use the results to recommend an appropriate fishway entrance velocity and fish lift operating schedule. PIT tagging was used to monitor fish rheotaxis for 48 h in four channels with differing flow characteristics. Swimming performance tests were conducted in a swimming respirometer and induced flow speed, critical swimming speed and critical burst speed were determined. The relationship between flow velocity and fish swimming behavior was analyzed to determine the optimal attraction flow velocity. There were three primary findings. (1) Test fish were active both day and night, but made more attempts, had longer retention times, and swam longer through-water distances in all channels during the day. (2) Entry, retention, and effort were maximum at a flow velocity of 0.2 m/s (26% of absolute critical swimming speed (m/s) and 29% of relative critical swimming speed (bl/s)). (3) Attempt number, retention time and through-water distance increased with body length in the channel with greatest activity. Collectively, these data suggest that passage of P. pingi will be optimized by fishways operating throughout the day and most of the night, although these conditions could lead to size-based selectivity in passage. [ABSTRACT FROM AUTHOR]

Retrofitting, or the addition of features to existing fishways to make them more suitable for upstream fish passage, is an issue of increasing interest in fishway science. Despite its potential for aiding fish passage, few studies are available on retrofitting of pool-and-weir fishways by adding boulders at the bottom of each pool of these facilities. The aim of this study was to assess the performance of a full-scale retrofitted pool-and-weir fishway model with boulders placed at the bottom of each pool, to enhance passage of a cyprinid species, the Iberian barbel ( Luciobarbus bocagei ), which was considered as a representative of medium-sized benthic potamodromous cyprinids in Iberia and Western Europe. Particular attention was given to testing the effects of boulder density and fishway discharge on passage success and fish transit time, both of which affect fish passage efficiency. Although no significant difference in passage success was detected between boulder spacings (mean proportion for high density: 35% success; mean proportion for low density: 40% success), increased flows (62.7 l/s) induced a higher mean proportion ( P < 0.05) of successful negotiations (50%), relative to low flows (38.5 l/s, 25%). With regard to fish transit time, under higher flows, fish took significantly less time ( P < 0.05) to ascend the fishway with the higher (5.3 ± 4.2 min) vs the lower boulder density (12.1 ± 6.5 min). This study showed that fish passage success was discharge-related and independent of boulder density. However, a high density boulder configuration combined with higher fishway discharge can be beneficial as it reduced fish transit time. Such information could be used to retrofit ill-functioning fishways in order to improve fish passage efficiency and negotiation of fishways for benthic potamodromous cyprinids. [ABSTRACT FROM AUTHOR]

Abstract: The construction of pool-type fishways has greatly increased in recent years in response to widespread river fragmentation by man-made structures. However, the performance of such facilities has often been questioned, particularly for non-salmonid fish fauna, which are frequently the predominant group of species found in rivers. This study presents the main findings from field and experimental research conducted over the last 10years on pool-type fishways in Portugal. Specific goals were: (i) to catalogue and evaluate the effectiveness of pool-type fishways built at small hydropower plants (SHP); (ii) to assess passage patterns of migrant fish populations through a “highly suitable” facility; (iii) to assess fish use for submerged orifices and surface notches under different flow regimes in experimental conditions and (iv) to determine the effect of hydraulic parameters on upstream movements of fish within these fishways. More than half (n =19, 51%) of the visited fishways were considered to be unsuitable for the target potamodromous species. Seasonal movements peaked in the spring (>70%) and occurred independently of time of day. Laboratory experiments showed a significantly greater proportion of movements occurring through submerged orifices rather than surface notches. Of all the analyzed hydraulic parameters, the Reynolds shear stress was the one that most influenced fish movements within the fishways investigated. The results of this study provide new information and insights that could have important implications on the design of future fishways, particularly for larger potamodromous cyprinids. [Copyright &y& Elsevier]

Turbulent flows are investigated in the bypass of a bar rack system to understand the effects of weirs placed at the bypass entrance on hydraulic conditions used to guide fish moving downstream. Three test cases were studied: (a) no weir (reference case), (b) arc-shaped weir and (c) triangular weir. A stereo particle image velocimetry system was employed to acquire the three velocity components in the mid-plane of the bypass and examine various statistics including mean velocities, Reynolds stresses, turbulent kinetic energy as well as turbulence eddies and swirling strength. The weirs deflect the flow away from the channel bed due to the blockage effect and increase the bypass velocity significantly, though remains under the suggested critical value of 1 m s−1 when the approach velocity was 0.38 m s−1. In the wake region of the triangular weir, a distinct recirculation bubble forms which may negatively affect fish migration. There is an increase in the level of Reynolds stresses and turbulent kinetic energy in the upstream vicinity of the weirs and the shear layers issuing from their tips. It is shown that the topology of the turbulence eddies is greatly modified by the weirs which can more readily assist fish guidance toward the bypass. Also, the swirling strength of the turbulence eddies behind the triangular weir is more pronounced compared to the arc-shaped weir. For the reference case, the swirling strength of the eddies is the weakest. • Effects of weirs at bypass entrance of bar rack systems on fish guidance effectiveness and swimming behavior are studied. • Key variables including velocities, spatial acceleration, Reynolds stresses, TKE as well as turbulence eddies are examined. • Mean velocities, spatial acceleration, Reynolds stresses and TKE enhanced significantly with the insertion of weirs. • Turbulence eddies are modified substantially around the weirs which helps fish pass downstream more readily. [ABSTRACT FROM AUTHOR]

Boulder submergence ratio may influence surrounding flow structures and as a result, local sediment transport as well as instream habitat preference. In this work, particle image velocimetry (PIV) measurements were used to study the effects of varying submergence ratios in Regimes 2 (1.3 < submergence ratio < 4) and 3 (1 < submergence ratio < 1.3) on the local flow field downstream of a boulder within a rock-ramp boulder array. It was found that in the wake of a boulder, the mean and turbulent flow characteristics for the lowest submergence ratio (Regime 3) varied substantially from the higher ones in Regime 2. From the variations of principal Reynolds shear stress and turbulent bursting events, a higher likelihood of intense downstream erosion was predicted for the lowest submergence ratio. Increased levels of mean velocity and turbulence also indicated that the local flow in the lowest submergence ratio may provide a less preferred habitat for fish. The findings suggest that based on the most common flow stages using a boulder size that generates higher submergence ratios in Regime 2 may improve the performance of stream restoration projects. [ABSTRACT FROM AUTHOR]

This paper presents an overall assessment of the hydraulics of a vertical slot fishway, the Vianney-Legendre vertical slot fishway on the Richelieu River in Quebec, Canada, which has been shown to be successful for passing a variety of fish species, including lake sturgeon. The fishway has a number of features that combine for a unique design. This includes two turning pools, shorter and narrower than recommended regular pools, and a low overall gradient. Detailed field measurements of the water levels and velocity patterns were obtained and a computational fluid dynamics modeling study was conducted. The model study evaluates the performance of various regular pool geometries based on fishway hydrodynamics. Low overall fishway gradient was shown to result in a fishway hydraulically suitable to fish passage, overcoming non-optimal pool dimensions. The relationship between discharge and corresponding average water depth in the pools, under both uniform and non-uniform flow conditions, using the discharge coefficient enabled us to simulate the distribution of water levels in a vertical slot fishway. Two distinct flow patterns were observed in a regular pool depending on the shape ratios between the pool's length and width. This study also assessed the spatial variation of velocity magnitude in the vertical plane to reveal regions of upwelling, downwelling, and the formation of eddies and dead flow zones that have potential importance for fish migration. [ABSTRACT FROM AUTHOR]

Experiments were performed in a novel pool & weir fishway to study the relationship between hydrodynamic and physiological parameters using rainbow trout (Oncorhynchus mykiss; mean TL = 15 cm). Fish were tested randomly using three fishway slopes (4, 7 and 10%) and three spacing ratios of W shaped weirs. Effect on fish hematology, immunology and stress were examined. Results showed that changing fishway hydraulic conditions altered fish stress levels. Increasing fishway slope and decreasing weir spacing, resulted in increased number of red blood cells and hematocrit, and decreased white blood cell count and serum lysosomes. In addition, levels of the most important stress indicator, cortisol, were elevated significantly compared to the control group, as slope, and consequently turbulence levels increased. Results showed that maximum turbulent kinetic energy (TKE) for a 10% fishway slope was increased to 0.22 m2/s2 while for a 4% slope and larger weir spacing was reduced to 0.05 m2/s2 which is the best condition for fish to rest in the pools created between the weirs. Observations on turbulence metrics showed that a weir spacing ratio of 6 offered the lowest gradients of energy changes. Furthermore, increasing the spacing ratio from 2 to 6 reduced cortisol levels and generally improved the physiological status of fish in the fishway. Considering turbulence levels at different depths of flow, the study concluded that physiological conditions for the passage of rainbow trout were best for a spacing ratio of 6 and a fishway slope of 4%. The evaluation of physiological metrics proved to be a vital and reliable process to integrate with hydrodynamics so fishway designs may be optimized to avoid stressing fish, and to enhance survival opportunities for migrating populations. • Physiological and hydrodynamic assessment of a novel fishway. • Slope, weir spacing, and flow turbulence affect fish passage. • Fish stress is associated with limits to turbulent flow metrics and key fishway design parameters. • Developed a physiological basis for improving fish migration solutions. [ABSTRACT FROM AUTHOR]