Turbulent flow field comparison and related suitability for fish passage of a standard and a simplified low‐gradient vertical slot fishway

Fishways are hydraulic structures that allow passage of fish across obstructions in rivers. Vertical slot fishways—VSFs—are considered the most efficient and least selective type of technical fishway solutions, especially due to their ability to remain effective even when significant upstream and/or downstream water level fluctuations occur. The scope of the present study is to perform numerical simulations in order to investigate and compare the hydraulic turbulent flow field in a standard and a simplified version of the most common VSF design. Implications in relation to fish swimming behaviour and fish passage performance are discussed. Different water depths (as well as discharges) were investigated, using a bed slope of 5%, as a reference for low‐gradient VSFs with a very limited selectivity that can be used in multispecies rivers in grayling‐barbel regions. Results show that maximum values of velocity, turbulent kinetic energy, and Reynolds stresses are higher in the standard design. However, corresponding to slot geometry and orientation, the direction of the main jet in the simplified design is more inclined towards the left side of the pool. This causes the eddy to split into 2 smaller ones; the minimum eddy dimension is reduced from 0.4–0.5 to 0.2–0.3 m. These dimensions are detrimental for fish passage efficiency, being more comparable with fish length (0.15–0.40 m), thus affecting migrating fish stability and orientation. Furthermore, the standard design provides a more straightforward upstream path and wider areas of low flow velocities and turbulence, useful for fish resting. Therefore, it is recommended that the standard design should be preferred over its simplified version, even if its construction costs are around 10–15% higher than the simplified one.     

An assessment of the effectiveness of a vertical‐slot fishway for non‐salmonid fish at a tidal barrier on a large tropical/subtropical river

Fishways for salmon in temperate rivers have often been successful, but salmonid‐type fishways for non‐salmonid species in tropical and subtropical rivers have frequently failed. This study assessed the effectiveness of modifying a salmonid‐type pool‐and‐weir fishway into a vertical‐slot design on a tidal barrage on the subtropical Fitzroy River, in Queensland, north‐eastern Australia. In 38 paired samples of the top and bottom of the fishway, over 16 months, 29 fish species and over 23 000 fish were collected at a maximum rate of 3400 per day. This study shows much greater potential for success with a vertical‐slot fishway as relatively few fish negotiated the original pool‐and‐weir design. Common species using the vertical‐slot fishway included blue‐catfish (Arius graeffei [Ariidae]), bony herring (Nematalosa erebi [Clupeidae]), striped mullet (Mugil cephalus [Mugilidae]), barramundi (Lates calcarifer [Centropomidae]), and long‐finned eels (Anguilla reinhardtii [Anguillidae]). Freshwater shrimp (Macrobrachium australiense [Palaemonidae]), juvenile crabs (Varuna litterata [Grapsidae]) and long‐finned elvers did not ascend the full length of the fishway and specific fishways for these species are recommended. Fish between 25 and 640 mm in length ascended the fishway, although the passage of smaller size classes of immature fish was restricted and this may be important for the sustainability of these migratory populations. The barramundi (200–640 mm) which ascended the fishway were all immature fish. However, during a period of low river flows enlarging the width of the vertical‐slot from 0.15 to 0.45 m only encouraged a small number of larger fish (890 mm maximum length) to enter. The strong diel movement patterns of many species will need to be considered in future fishway design. Blue‐catfish could ascend the fishway in 2 h, but many fish remained in the fishway and this behaviour may cause crowding and a reduction in fishway capacity. Further work is needed to assess the proportion of fish finding the fishway entrance. However, the findings suggest that vertical‐slot fishways with lower water velocities and turbulence than salmonid fishways have great potential to pass the diverse migratory fish fauna of subtropical and tropical rivers. Copyright © 1999 John Wiley & Sons, Ltd.     

齐口裂腹鱼幼鱼在竖缝式鱼道模型中的上溯行为研究

为了解齐口裂腹鱼在鱼道中的上溯情况,在大比尺竖缝式鱼道物理模型中开展了以齐口裂腹鱼幼鱼为过鱼对象的过鱼试验研究。试验中对通过时间、通过率和上溯轨迹进行了记录,并运用Spearman秩相关分析对齐口裂腹鱼的上溯轨迹和池室结构的水力因子(流速、紊动能、总水力应变)进行了分析。研究发现,试验用鱼通过时间平均值为132.7s,多数鱼倾向于快速通过鱼道完成上溯。试验鱼道通过率为71.9%,过鱼效果良好。多数齐口裂腹鱼上溯过程中会避开高流速区、高紊动能区和高水力应变区,在池室内齐口裂腹鱼上溯轨迹主要分布于上述参数较低的右侧回流区和隔板背水面,竖缝断面处多数齐口裂腹鱼选择上述参数相对较低的隔板侧区域通过。研究结果可为相关竖缝式鱼道设计和实践提供参考。     

竖缝式鱼道水力特性与鱼类运动特性相关性分析

竖缝式鱼道(Vertical Slot Fishway,VSF)作为一种协助上溯性鱼类恢复其洄游通道的生态补偿措施,受到广泛关注。其过鱼效果与VSF的水力特性和鱼类的游泳运动能力密切相关。因而,良好的VSF设计应保证池室内的水力特性与过鱼对象的游泳运动能力相适宜。本文选取上溯性鱼类鳙鱼和草鱼为研究对象,将VSF池室内水力因子空间分布与鱼类运动轨迹相叠加,定量分析了鳙鱼和草鱼在上溯过程中的运动特性、水力偏好以及鱼类运动轨迹与特定水力因子的相关程度。试验结果表明:在流量为0.135 m3/s的VSF池室内,两种鱼喜好在紊动能为0.02~0.035 m2/s2、流速为0.16~0.4 m/s、紊动耗散率为0.02~0.04 m2/s3、应变率为2~3.5 s-1的范围内运动。鳙鱼和草鱼在不同水力区域内的上溯时间与紊动能、流速相关性较大;水流流速矢量体现鱼的趋流特性,决定了鱼的上溯方向,而对于局部空间内鱼的游泳运动行为,紊动能可能是影响更直接的水力因子。     

Implications of an invasive fish barrier for the long‐term recovery of native fish assemblages in a previously degraded northeastern Illinois River system

Barriers to fish movement have been used to prevent the spread of invasive fishes but may also limit the movements of native fishes. We evaluated the potential consequences of a proposed barrier on the Illinois River Waterway, meant to inhibit the spread of silver and bighead carps, to the continued recovery of native fishes in the Des Plaines River following water quality improvements. We compared changes in upstream cumulative species richness and community structure from 1983 to 2013 in the DuPage River, an adjacent tributary with an impassable dam, to the area upstream of a newly proposed barrier on the Des Plaines River where fish can currently pass through a navigational lock. Fewer species displayed truncated distributions upstream of the passable lock and dam (n = 18) compared with the impassable dam (n = 23). Due to water quality improvements in the Illinois River as a whole, cumulative species richness downstream of both dams steadily increased over time. Richness also increased upstream of the passable dam but plateaued upstream of the impassable dam. Fifteen to 18 species accounted for differences in community structure between areas downstream and upstream of either dam. Most species (78–100%) were found in greater relative abundance downstream of the impassable dam, and only 53% were found in greater relative abundance downstream of the passable dam. The truncation in species richness and abundance at the impassable dam foreshadows the potential consequences of an indiscriminate barrier on native fishes and the continued recovery of native assemblages.     

Monitoring upstream fish passage through a Mississippi River lock and dam reveals species differences in lock chamber usage and supports a fish passage model which describes velocity‐dependent passage through spillway gates

Nearly 200 fish were released below Lock and Dam 2 (LD2) in the Upper Mississippi River and tracked to determine both whether and how they passed through this structure, and if passage could be explained using a computational fish passage model (FPM) which combines hydraulics with fish swimming performance. Fish were either captured and released downstream of LD2 in Pool 3 or captured in Pool 2 (upstream of LD2) and displaced below LD2. Tagged fish were tracked using 13 archival receivers located across LD2. Approximately 90% of all fish approached LD2 many times with the displaced species likely attempting to home. Of 112 common carp, 26% passed through LD2 with 15% (most) going through the lock and 6% through the spillway gates. Similar values were seen for bigmouth buffalo. In contrast, although 42% of 31 channel catfish passed through the lock, only 3% went through the gates. Finally, of 22 walleye, only 14% passed through the lock and none through the gates. Ninety percent of all documented passages through the spillway gates occurred when the gates were out of the water and water velocities through these gates were at their lowest levels, an attribute described and predicted by the FPM at LD2. This study strongly suggests that fish passage through spillway gates of LDs is determined by water velocity and can be predicted with a FPM, whereas passage through locks is determined by species‐specific behavioural preferences. Both attributes could be exploited to reduce passage of invasive carp at certain locations.     

Performance of a fishway system in a major South American dam on the Parana River (Argentina–Paraguay)

Successful design and operation of fish passage systems are important to protect fish communities from impacts of hydroelectric dams in the Río de la Plata River basin. We evaluated the performance of an elevator lift system to pass adult fish through Yacyretá dam on the Paraná River between 1995 and 1998, both for mechanical reliability and performance. The elevator lift system was mechanically inoperative 30–38% of the time during the October–December period of greatest fish migration. Target species represented 30% of total fish number in gillnet samples in the tailwater, but constituted only 10% of the total number of fish transferred. Fish collected within the system were dominated by Pimelodus clarias (>69%), although this species represented less than 10% of captures in experimental gillnets set in the tailwater. Prochilodus lineatus, a key species, represented less than 5% of transferred fish, but constituted 22.1% of tailwater samples. Estimated number of fish transferred per year ranged between 1 210 000 (1995) and 3 610 000 (1996) with biomass ranging from 631 to 1989 tons, respectively. We estimated a fish passage efficiency of 1.88% for all species and 0.62% for target species. At this efficiency, transferred species would increase the total fish yield in the reservoir by as much as 4.9 kg/ha/year, but only 0.5 kg/ha/year for target species. We conclude that fish transfer efficiency is inadequate to maintain populations of target species in the Paraná River system. We identify critical research needs to improve the passage of fish at dams. Copyright © 2002 John Wiley & Sons, Ltd.     

Evaluation of nature‐like fishways for re‐establishing connectivity in fragmented salmonid populations in the River Emån

We evaluated the function of two nature‐like fishways for re‐establishing connectivity for anadromous salmonids in the regulated River Emån. Between 90 and 100% of the salmonids that entered the fishways actually passed through them, with median speeds of 180–190 m h^?1. Only 50% of the anadromous brown trout that passed the first fishway also passed the second one, indicating that the fish might have had problems locating the upstream fishway. The fishways were also observed to function as a passage for downstream post‐spawning migrants. The densities of brown trout yearlings upstream of the fishways were higher in 2002, after the fishways were built, than during pre‐fishway years. In control sites in other parts of the river as well as in a nearby river, no changes in yearling densities were observed. Thus, the fishways are working for upstream spawners, albeit at a recolonization rate that is slower than expected. Copyright © 2005 John Wiley & Sons, Ltd.     

Age,growth and non‐flood recruitment of two potamodromous fishes in a large semi‐arid/temperate river system

Golden perch Macquaria ambigua (Percichthyidae) and silver perch Bidyanus bidyanus (Terapontidae) are two potamodromous fish species of the Murray‐Darling river system in southeastern Australia. Ageing of these species using thin sections of the sagittal otoliths and validation with known‐age fish revealed: they live for over 26 years; male and female silver perch reach maturity at 3 and 5 years respectively; male and female golden perch reach maturity at 2 and 4 years respectively; both species exhibit sexual dimorphism with larger females; and growth varies (L_∞ silver perch 331–397 mm, golden perch 354–502 mm) among interconnected river systems. Longevity and opportunistic growth are characteristics that are well suited to the semi‐arid and temperate hydrology of this river system. A flood‐recruitment model for these two species, consistent with the ‘flood‐pulse concept’, has previously been assumed to be the main mechanism of recruitment. The model appeared appropriate for this large, low‐gradient river system with productive floodplains. However, in the middle reaches of the Murray River we found that golden perch recruitment was strong in non‐flood years and poor in flood years, and silver perch recruited in all years. These data do not preclude golden perch recruiting during floods as well, because downstream larval drift may have resulted in strong year‐classes being swept downstream of the sampling area during high flows. However, the recruitment models for these species need to be re‐evaluated to include within‐channel flows. Importantly, these flows can be manipulated by river regulation, unlike large floods, and therefore there is potential to enhance recruitment. Copyright © 2003 John Wiley & Sons, Ltd.     

Spatial patterns of fish communities in the Upper Mississippi River System: assessing fragmentation by low‐head dams

We assessed the similarity of fish communities among river reaches to assess community‐level fragmentation by low‐head dams in the Upper Mississippi River System (UMRS). The spatial coverage of standardized electrofishing sampling used in the Long Term Resource Monitoring Program (LTRMP) was extended for three of the six regional trend areas (RTA; pools 4, 13, and the Open River Reach) to include river reaches (outpools) immediately upstream and downstream from the standard RTA from 15 June to 31 October 2000. Additionally, pools 19 and 20 were sampled in September 2000. Cluster analysis and non‐metric multidimensional scaling of community composition and structure data revealed two major groups, upper and lower reaches, and four (for composition) or five (for structure) sub‐groupings of river reaches. In general, all outpools grouped with the nearest RTA for both community composition (no exception) and community structure (one exception). This suggests that fragmentation of fish communities from low‐head dams is minimal. Mantel correlations demonstrated strong inverse association between the similarity of fish communities with the distance between reaches. Habitat variables measured during electrofishing collections were significantly correlated with spatial variation of fish composition and community structure, but provided only marginal improvements to correlations with distance between reaches alone. Furthermore, habitat variability among river reaches also was related to distance between reaches. Determining the extent to which variation of fish communities is related to habitat or demographic processes (e.g. migration, larval drift, source‐sink dynamics) will be challenging for this system. Although low‐head dams on the UMRS may restrict movements for individuals and populations of certain fish species, we found little evidence that these effects have led to substantial, community‐level fragmentation. Copyright © 2006 John Wiley & Sons, Ltd.     

Site fidelity and movement of a small‐bodied fish species,the rainbow darter (Etheostoma caeruleum): Implications for environmental effects assessment

Small‐bodied fish species are commonly used for the assessment of environmental effects because they are short lived, abundant, and they mature early. Although they are generally considered to be less mobile than larger bodied species, relatively little is known about their movement patterns. In this study, we tagged 3,001 rainbow darters (Etheostoma caeruleum) (≤76 mm) in the upper Grand River of southern Ontario with visible implant alpha tags and elastomers in 3 riffles. Five hundred sixty‐five fish were recaptured over 4 recapture events (including spawning and nonspawning periods) over a spatial extent of 1900 m. The rainbow darter demonstrated high site fidelity having a median movement of 5 m and with 85% staying within the riffle in which they were originally tagged. Most movements occurred during the spawning period, where males moved at a greater frequency and had a tendency to move longer distances (up to 975 m). There was also a bias in the direction of movement, which was dependent on the recapture season. Overall, the high site fidelity of the rainbow darter makes it a candidate, sentinel species for the assessment of environmental effects.     

Effects of water velocity and turbulence on the behaviour of Iberian barbel (Luciobarbus bocagei,Steindachner 1864) in an experimental pool‐type fishway

The restoration of fish passage has been focused on anadromous fish species, whilst studies accommodating passage of coarse species have often been considered incidental, yet frequently these are the predominant group of species encountered in rivers. In addition, fishway designs depend greatly on the interplay between hydraulics and biomechanics, yet very little data are available on the responses to specific hydraulic settings for these species. This study aims to explore the effects of water velocity and turbulence on the behaviour of a cyprinid species ‐ the Iberian barbel Luciobarbus bocagei (Steindachner, 1864) ‐ particularly their upstream movements upon different discharges (38.5 to 77.0 L · s^?1), through an indoor full scale pool‐type fishway prototype. Larger adults had a higher passage success (mean = 79%) and took less time (mean ± SD (min): 5.7 ± 1.3) to negotiate the entire six pool fishway, when compared to small adults. Correlation analysis between hydraulic variables and fish transit time yielded different results. Correlations were found to be the highest between the horizontal component of Reynolds shear stress and fish transit time, particularly for smaller size‐individuals (r = ?0.45; p < 0.001), highlighting this variable as a key‐parameter which strongly determines the movements of Iberian barbel. The present study identified key factors on Iberian barbel movements that may have direct application to future fishway designs for this species and for other ‘weak’ swimmers. Copyright © 2010 John Wiley & Sons, Ltd.     

Three‐dimensional numerical simulations of smooth,asymmetrically roughened,and baffled culverts for upstream passage of small‐bodied fish

Traditional box culvert designs lead to development of high velocity zones in the culvert barrel that often impede upstream migration of fish. Herein, three‐dimensional Reynolds‐averaged Navier‐Stokes (RANS)‐ and Large eddy simulation (LES)‐based computational fluid dynamics (CFDs) simulations were performed to compare the effectiveness of smooth, asymmetrically roughened, and corner‐baffled barrels, in creating low‐velocity zones (LVZs) and providing opportunity for upstream passage of small‐bodied fish. The results revealed distinctive benefits provided by the asymmetrically roughened and corner‐baffled barrels relative to the smooth barrel. Cross‐sectional asymmetry, corners, and obstructions are important factors that contribute to the generation of LVZs conducive to fish passage, albeit contiguity of LVZs is required, particularly for weak swimmers. The study demonstrates the adequacy and effectiveness of CFD models to complement traditional laboratory studies in understanding basic mechanisms beneficial to fish passage and to provide insights into future designs.     

Effects of dams in river networks on fish assemblages in non‐impoundment sections of rivers in Michigan and Wisconsin,USA

Regional assessment of cumulative impacts of dams on riverine fish assemblages provides resource managers essential information for dam operation, potential dam removal, river health assessment and overall ecosystem management. Such an assessment is challenging because characteristics of fish assemblages are not only affected by dams, but also influenced by natural variation and human‐induced modification (in addition to dams) in thermal and flow regimes, physicochemical habitats and biological assemblages. This study evaluated the impacts of dams on river fish assemblages in the non‐impoundment sections of rivers in the states of Michigan and Wisconsin using multiple fish assemblage indicators and multiple approaches to distinguish the influences of dams from those of other natural and human‐induced factors. We found that environmental factors that influence fish assemblages in addition to dams should be incorporated when evaluating regional effects of dams on fish assemblages. Without considering such co‐influential factors, the evaluation is inadequate and potentially misleading. The role of dams alone in determining fish assemblages at a regional spatial scale is relatively small (explained less than 20% of variance) compared with the other environmental factors, such as river size, flow and thermal regimes and land uses jointly. However, our results do demonstrate that downstream and upstream dams can substantially modify fish assemblages in the non‐impoundment sections of rivers. After excluding river size and land‐use influences, our results clearly demonstrate that dams have significant impacts on fish biotic‐integrity and habitat‐and‐social‐preference indicators. The influences of the upstream dams, downstream dams, distance to dams, and dam density differ among the fish indicators, which have different implications for maintaining river biotic integrity, protecting biodiversity and managing fisheries. Copyright © 2010 John Wiley & Sons, Ltd.     

Selective use and spatial distribution of native and non‐native fish in wetland habitats

Wetland habitats are crucial for many fish species as spawning, feeding or nursery areas, but the major factors that govern their use by fish are poorly identified. In the present study, we aim to investigate the selective use and the spatial distribution of native and non‐native fish species in different types of wetland habitats (grasslands and reed beds) in a large freshwater marsh (North Western France). The selective use was measured by comparing the community that uses wetland habitats to the total community of the marsh (sampled in the permanent aquatic habitats (canals) during the low water period). The spatial distribution was studied by analyzing the presence probability of fish in wetland habitats as a function of the distance from adjacent canals. All sampled wetland habitats were occupied by fish, and the fish community in wetland habitats was dominated by three native (Abramis brama, Scardinius erythrophthalmus and Anguilla anguilla) and three non‐native (Ameiurus melas, Gambusia holbrooki and Lepomis gibbosus) species. Species richness and total fish abundance differed between canals and wetland habitats as a consequence of a variable propensity to use wetland habitats by native (avoidance and preference) and non‐native (no preference) species. Non‐native species were also more abundant in reed beds than in grassland while no differences were observed for native species. Universally, the presence probability of fish always decreased in wetland habitats as the distance from the canals increased and only a narrow area, close to canals (50–80 m), was well used by fish. However, non‐native fish species used over greater distances in reed beds than in grasslands while no differences were observed for native species. Variable interpretations related to species tolerance, reproductive guilds or diet are proposed to understand the mechanisms that might explain the widespread success of non‐native species in this spatially varying environment. Copyright © 2008 John Wiley & Sons, Ltd.     

Hydraulic assessment of environmental flow regimes to facilitate fish passage through natural riffles: Shoalhaven river below Tallowa Dam,New South Wales,Australia

Proposed environmental flow regime changes downstream of a major water supply dam have been assessed in terms of effects on depth, velocity and fish passage across natural, gravel‐bed riffles and rapids. This study focussed on passage requirements for Australian bass, Macquaria novemaculeata (Perciformes, Percichthyidae), a catadromous fish of considerable ecological and recreational fishing importance. Some 23 major riffles and rapids occur between the dam and the tidal limit over a river length of 25 km. Reconnaissance investigations of riffle slope, length, width, depth and morphologic characteristics indicated that wide‐shallow, steep‐turbulent and bifurcating riffle morphologies were most likely to cause problems for upstream bass passage under low flow conditions. Two approaches were used to investigate riffle depths and velocities over a range of flows. A rapid assessment approach directly measured thalweg depths and velocities under two controlled flow release rates in riffles identified as being potentially problematic to upstream bass passage. Detailed topographic surveys and two dimensional hydraulic modelling with River2D was undertaken for two riffles identified as ‘worst case’ examples of wide‐shallow and steep‐turbulent morphologies. Results from both approaches were consistent and complementary. Both approaches identified riffles where minimum depths and maximum velocities were likely to be problematic for upstream passage by Australian bass at a flow rate of 130 MLd^?1 (the current regulated flow release) but were mitigated at flow rates above 300 MLd^?1. Assessment of environmental flow regime transparency and translucency threshold options with regard to a 300 MLd^?1 target flow indicated that options where the transparency threshold was set at the 80th flow duration percentile (flows equalled or exceeded for 80% of time), and varied according to the monthly pattern of natural flows, improved hydraulic conditions for upstream bass migration. Copyright © 2009 John Wiley & Sons, Ltd.     

Patterns in groundwater nitrogen concentration in the riparian zone of a large semi‐arid river (River Murray,Australia)

Lateral exchanges of surface water between river channels and their floodplains are important for vegetation health and aquatic food‐web productivity in semi‐arid ecosystems. However, the significance of the lateral connectivity via sub‐surface pathways in these systems is not as well understood. Patterns in nitrogen concentration in groundwater and in the unsaturated zone were used to infer the sub‐surface biogeochemistry of N in the riparian zone of a large semi‐arid floodplain (Hattah‐Kulkyne National Park) of the River Murray, Australia. The riparian zone plays a special role in this system as it is an area of transition between fresh surface waters and saline floodplain groundwater. The river was losing water to the floodplain during baseflow conditions but gradients were temporarily reversed following floods. In general, the redox conditions were sub‐oxic to anoxic in riparian groundwater and the main forms of N present were NH and dissolved organic N. There was a gradient in NH concentration from the river to the floodplain, suggesting that the main source of NH was from the decomposition of organic matter in fluvial sediments. Elevated concentrations of NO were occasionally found in shallow groundwater away from the river following floods but tended not to persist. The source of the NO appeared to be unsaturated‐zone NO displaced to the water table during floods. Assuming that denitrification was the main attenuation process, this displacement of unsaturated zone NO to anoxic groundwater could be a significant N removal process from the ecosystem (estimated at 18 kg N ha^?1 for the largest flood during the study). Understanding the impact of river regulation on floodplain nutrient cycles in River Murray floodplains will be challenging because the changes in floodplain hydrology are complex and coincide with salinization of soils and groundwater. Copyright © 2005 John Wiley & Sons, Ltd.