Body size,experience, and sex do matter: Multiyear study shows improved passage rates for alewife (Alosa pseudoharengus) through small‐scale Denil and pool‐and‐weir fishways

Alewife (Alosa pseudoharengus) passage through 3 fishways was assessed during the 2013–2016 spawning runs in 3 rivers of the Isthmus of Chignecto, Canada. From April 24 to June 10, 5,423 alewife with a mean ± SD fork length of 227 ± 18 mm were tagged with passive integrated transponders. During their tagging year, approximately half of individuals (40% to 64%) went undetected whereas those detected used fishways from April 16 to July 8. Detected alewife were significantly longer than those undetected. Attraction rates to fishway entrances in 2015 and 2016 ranged from 85% to 98%. Annual fishway passage rates for pooled fish tagged that year and returnees, varied from 64% to 97% for 2 Denil style fishways. A pool‐and‐weir fishway that was dysfunctional (2013), repaired (2014), and replaced (2015–2016) yielded 0.5%, 25%, 60%, and 73% annual pooled passage rates, respectively. Larger individuals, previously tagged returnees, and males compared to females of a similar size had higher passage success suggesting some fishways may apply population‐level selective pressures. Alewife passage rates related to fishway style, design, and proper function, with greater passage for the 2 Denils than the pool‐and‐weir fishway in our study. Regular structural maintenance and fish passage reviews are essential management considerations to ensure fishway functioning and river connectivity. Replacement of a fishway with poor fish passage may be the best option to improve passage rates. Future research should address the effects of multiple anthropogenic instream obstructions, environmental variables, negative sublethal post‐tagging effects, and the importance of returnees on fish passage rates in fishways.     

USING AN EXPERIMENTAL IN SITU FISHWAY TO PROVIDE KEY DESIGN CRITERIA FOR LATERAL FISH PASSAGE IN TROPICAL RIVERS: A CASE STUDY FROM THE MEKONG RIVER,CENTRAL LAO PDR

Fish passage through an experimental vertical‐slot fishway was assessed at a floodplain regulator on the Mekong River in Central Laos between April and July 2009. Experiments were conducted to investigate the influence of fishway floor slope (1v:15h or 1v:7.5h) on fish passage success with a view to developing a series of optimal design criteria for the construction of vertical‐slot fishways at other barriers to fish passage in the Lower Mekong Basin. A total of 14 661 fish from 73 species were captured during the experiments. Catches were dominated by riverine (white) (n = 51; 69% of total) and floodplain (black) species (n = 15; 20%) which represented 19 families in total. The work demonstrated that fish were actively attempting upstream passage from the Mekong River to an adjacent floodplain and displayed strong migratory behaviour during river level rises. Migratory activity was greatest during sharp rises in water level but reduced substantially when river level fell. Fish community composition varied greatly among the two fishway floor slopes and the control group. More fish species were collected from control samples, but the most fish and species were collected when the fishway was configured on a moderate hydraulic slope (1v:15h). A range of size classes were also collected from control and moderate‐slope groups, but steeper‐gradient catches were dominated by larger fish. This study demonstrated that vertical‐slot fishways could provide passage for a biodiverse fish community where fish move laterally onto floodplains. The construction of fishways which consider the local fish ecology and hydrology may therefore represent a valuable management tool to help restore important movement pathways for tropical freshwater fish. Copyright © 2011 John Wiley & Sons, Ltd.     

Attraction and passage efficiency for salmonids and non-salmonids based on fishway: A meta-analysis approach

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.     

Survey on performance of vertical slot and nature-like fishways at Angu hydropower station,Southwest China

To restore dam-blocked natural fish migratory passages, a growing number of artificial fishways have been built in water conservancy and hydropower projects in China. The Angu hydropower station involved diverse important fish habitats in the lower reaches of the Daduhe River in Southwest China. Therefore, a vertical slot fishway (VSF) and a nature-like fishway (NLF) were built near the backwater area of the reservoir to connect the upstream and downstream habitats. Hydrodynamic and aquatic ecological surveys were conducted after the completion of the project to estimate the fish passing effect of the two fishways. The results indicated that both fishways were in effective operation and could maintain the desired hydrodynamic conditions and be used by several local fish species. During the survey, 149 fish from 15 species and 111 fish from 17 species were captured by the traps in the VSF and NLF, respectively, while 1 263 fish from 27 species were found in the downstream area. Some species captured in the VSF were not found in the NLF, and vice versa, which implied the different preferences of fish. Meanwhile, 3 789 signals including 2 099 upward ones and 1 690 downward ones were monitored with an ultrasonic fish detector at the inlet of the VSF. These findings revealed the characteristics of fish species observed in and near the fishways and provided valuable insights into the different fish passing capabilities of VSF and NLF.

     

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.     

Do fish locks have potential in tropical rivers?

This study evaluated attraction and passage of native fish through an automated fish lock on the tropical Fitzroy River in north‐eastern Australia. In 69 samples (24 h each) taken at the exit and entrance of the fish lock, 17 fish species and 13 402 individuals were collected, at a maximum rate of 3317 fish per day. During low river flows, the fish lock transferred a broad size range of fish (35–710 mm long), though migratory biomass was small. Removal of a vertical fish‐crowding device did not affect the passage rate. Netting studies and observations of fish migrating below the weir suggested that the entrance was poorly located during high flows and another fishway near the spillway would enhance fish passage. The fish lock was inoperative for 48% of the time, due to mechanical and software failure, and a narrow operational range unsuited to the variable hydrology. Nevertheless, these design issues are site specific and reflect that fish lock technology is in its infancy in Australia. The operational reliability of the fish lock is now greatly improved but further work is needed to optimize the automatic cycling. To accommodate the inherently variable hydrology of lowland tropical/sub‐tropical rivers into fishway design, we highlight important research needs for fishways and migratory fish communities. Fish locks are often considered a less favourable fish passage option but with the operational reliability issues partially resolved, they appear to have considerable potential for tropical river systems with low minimum flows and low biomass; with further research and design, they may have wider application. Copyright © 2007 John Wiley & Sons, Ltd.     

Not just a migration problem: Metapopulations,habitat shifts,and gene flow are also important for fishway science and management

Worldwide, fishways are increasingly criticized for failing to meet conservation goals. We argue that this is largely due to the dominance of diadromous species of the Northern Hemisphere (e.g., Salmonidae) in the research that underpins the concepts and methods of fishway science and management. With highly diverse life histories, swimming abilities and spatial ecologies, most freshwater fish species do not conform to the stereotype imposed by this framework. This is leading to a global proliferation of fishways that are often unsuitable for native species. The vast majority of fish populations do not undertake extensive migrations between clearly separated critical habitats, yet the movement of individuals and the genetic information they carry is critically important for population viability. We briefly review some of the latest advances in spatial ecological modelling for dendritic networks to better define what it means to achieve effective fish passage at a barrier. Through a combination of critical habitat assessment and the modelling of metapopulations, climate change‐driven habitat shifts, and adaptive gene flow, we recommend a conceptual and methodological framework for fishway target‐setting and monitoring suitable for a wide range of species. In the process, we raise a number of issues that should contribute to the ongoing debate about fish passage research and the design and monitoring of fishways.     

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.     

Are smallmouth bass more mobile in large lakes than once thought?

Smallmouth bass Micropterus dolomieu are generally considered to be a sedentary species. Previous tagging studies in lentic systems have found low annual movements based on fishery-dependent tag returns or limited detections from electronic transmitters, though occasional long-distance movements have been observed (i.e., >30 km). In this study, we implanted 23 smallmouth bass sampled from a recreational tournament in Lake Erie with acoustic transmitters and monitored their movements for two years (September 2018–September 2020) using a large-scale array of passive acoustic receivers. We documented 42 percent (8/19) of the at-large fish making long-distance movements throughout Lake Erie; these fish moved an average distance of 109.9 ± 26.6 km (mean ± SE; ranging 3.5–355.1 km) per year. Importantly, six of eight fish crossed jurisdictional boundaries (five into Ontario waters and one into Michigan waters). One individual moved a total of 505.3 km over the two years, the furthest distance an individual smallmouth bass has been documented moving across the literature. While observed movements may have been initially biased due to tournament displacement and capture method, tagged fish continued to make long-distance movements in the second-year post-release. Previous movement studies may have underestimated smallmouth bass movement scope in large, lentic systems due to low spatial and temporal coverage of recapture effort (including receiver coverage) relative to system size. Our results suggest that some smallmouth bass can make consistent long-distance movements in large systems like the Laurentian Great Lakes, indicating this species’ spatial ecology remains understudied in large lentic systems.     

鱼道水力特性研究进展

综述竖缝式、池堰式和涵洞式、丹尼尔式及组合式鱼道水力特性的国内外研究进展;对比分析水流流态、流速场特征、流量与水深的关系、紊流特性及消能率等几方面对不同鱼道的水力特性的影响;得出了竖缝式鱼道中无量纲流量与相对水深之间呈线性关系的结论,列出了池堰式鱼道中流量与水深的关系式;指出鱼道中紊流的紊动能、紊流强度及紊流结构均会对鱼道水力特性、鱼类对栖息地的选择以及鱼类通行造成较大影响;展望鱼道未来研究重心会逐渐集中于鱼道内紊流特性及其数值模拟的研究,尤其是紊流结构的研究。此外,不同结构形式鱼道内水力条件对鱼类通行的影响及改善措施亦将成为未来研究热点之一。     

Numerical study of the effect of a V-shaped weir on turbulence characteristics and velocity in V-weir fishways

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.     

Post-tournament dispersal of smallmouth bass in western Lake Erie

Catch-and-release tournaments for smallmouth bass Micropterus dolomieu transport fish from many capture locations to a centralized release site. In the Great Lakes, these fish may be transported long distances (i.e., >100 km) and subsequently become concentrated at a release site, possibly negatively affecting subpopulations at popular fishing sites if fish remain concentrated in the area. To assess timing of post-tournament dispersal, 23 smallmouth bass were implanted with acoustic transmitters and released into Sandusky Bay (Lake Erie) after a large tournament (50 boats) in September 2018. Tagged fish were tracked via a grid of acoustic receivers. All surviving fish (n = 19) left the immediate vicinity of the release site (<500 m) after an average (±SE) of 13.2 (±2.4) d, with many (58%) returning to the main lake (19.7 d ± 3.4). Eight (42%) of the surviving fish left the release site but remained in the bay after 50 d. Based on the results from this study, long-term (>1 month) concentration of smallmouth bass at release sites is unlikely to be a problem for Lake Erie bass tournaments, but temporary (up to 1 month) accumulations of fish are possible. A fraction of tournament-released smallmouth bass resided in Sandusky Bay for extended periods (>2 months), which could be considered functionally harvested from main lake subpopulations. Currently, the frequency of bass tournaments on Lake Erie is uncertain, and better documentation of tournament frequency and scale is necessary to assess potential negative impacts on bass populations.     

Connectivity is a two‐way street—the need for a holistic approach to fish passage problems in regulated rivers

We evaluated the effects of a rehabilitation project, whose goal was to re‐establish longitudinal connectivity for anadromous trout in the regulated river Emån. We used a holistic approach, by tagging and following both upstream‐migrating spawners (N = 348) and downstream‐migrating smolts (N = 80) and kelts as they passed two hydroelectric plants (HEP 2‐3) with nature‐like fishways. When migrating upstream, 84–88% of the spawners stopped, primarily at spawning grounds, before reaching HEP2. The proportion of stoppers was lower (56%) for fish that had been to the fishways in previous years, indicating that the recolonization rate is likely to increase over time. Of the spawners that approached the fishway at HEP2, 77% rapidly located the fishway situated next to the tail‐race, resulting in an attraction efficiency of 81% and a passage efficiency of 95%. The time required to locate the fishway inside the former channel at HEP3 was substantial, but the attraction efficiency (89%) and passage efficiency (97%) were nevertheless high. The kelts swam downstream mainly in spring, using spill gates and the fishways, to swim past HEP2 and 3 and continue downstream to the Baltic Sea. Iteroparity was confirmed by the fact that 20% of the spawners were tagged in previous years. Smolt loss was about 30% for both HEPs, with a higher turbine‐induced loss 30% for fish passing through Francis runners than a Kaplan runner. Fifteen per cent of the tagged smolt reached the sea and none of these fish had swum through the Francis runners. It will probably take many years before longitudinal connectivity is fully re‐established in the river Emån, due to substantial losses of both upstream‐migrating spawners (35% loss) and downstream‐migrating smolts (50%) and kelts. In addition, smolt production in areas upstream of HEP3 is far below carrying capacity. Thus, additional measures that not only facilitate movement of upstream spawners, but also reduce mortality and injuries of downstream migrants are urgently needed to create a self‐sustaining fish population. Copyright © 2009 John Wiley & Sons, Ltd.     

Movement of three non‐salmonid fish species through a low‐gradient vertical‐slot fishway

Well‐designed fishways have assisted in restoring migrations and rehabilitating riverine fish species in all continents. The performance of fishways varies greatly with their type, design and operating regime, and with the species involved. Vertical‐slot fishways are widely used to overcome low‐level barriers, especially for non‐salmonids. Important issues remain in the design of fishways to meet performance and cost criteria, including the relationship between fishway bed gradient and the fish that ascend, and whether resting pools are needed. Models of species' movement patterns can inform fishway designers about likely fish response to various design options, and can lead to improved efficiency and effectiveness. Models of general movement patterns of three potamodromous non‐salmonid fishes in the Murray River, Australia, were developed from empirical data in a low‐gradient vertical‐slot fishway. The models integrate data on times of entry and exit, ascent rates, and whether fish continued to ascend during the night. These fish species did not favour resting pools. Ascent rates of fish ≥120 mm were more closely related to fish behaviour than to length; for a given fishway height, reducing bed slope by increasing the number of pools may slow the ascent of such fish, whereas enlarging pool volumes increases costs. Copyright © 2010 John Wiley & Sons, Ltd.     

Migratory fishes of Brazil: Life history and fish passage needs

Many of the most important commercial and recreational species of the megadiverse Brazilian freshwater fishes migrate in rivers among essential habitats during all life stages. These movements, however, have been severely blocked by hundreds of hydroelectric dams and reservoirs and they will be even more obstructed due to hundreds of new developments. Fishways have been used in many countries to allow fish to pass around dams. Fishway construction is booming in Brazil, but poor understanding of migrations by Brazilian fishes has led legislators, scientists, and the public to several misconceptions about the rules of fishways in fisheries conservation. First, is a belief that fishways are only needed to facilitate upstream spawning migrations. Also, it has been suggested that upstream passage for Neotropical migrant fishes is not useful if there is no large free‐flowing stretch upstream of a dam that contains spawning habitat and has a large natural floodplain (nursery habitat). In this paper, we discuss that, in addition to providing passage for pre‐spawning migrants, upstream fishways also provide passage for other fish migrations (e.g. foraging), and that all up‐ and downstream migrations during life history need to be addressed at dams to conserve fish resources. We also argue that an upstream fishway is important even if the upstream reach does not have spawning or nursery habitats. In addition, we discuss the need for protection of downstream migrant fish, and the importance of fish behaviourists and engineers working together on fishway design and operation to solve fish passage issues. Copyright © 2008 John Wiley & Sons, Ltd.     

Hydropower Development,Riverine Connectivity,and Non‐sport Fish Species: criteria for Hydraulic Design of Fishways

Hydropower barriers are among the most conspicuous anthropogenic alterations to natural riverine connectivity, resulting in species‐specific effects linked to dispersal abilities, especially swimming performance. They may present a particular problem for small‐bodied ‘non‐sport fish’, such as those that characterize the freshwater communities of temperate regions in the Southern Hemisphere. Recent studies have suggested that nature‐like fishways could ensure passage of diverse fish assemblages through hydropower barriers. Through experiments performed in a swim tunnel, we present, for the first time, fishway design criteria for two non‐sport species endemic to Chile, a country experiencing rapid hydropower development. In`cremental velocity tests showed that Cheirodon galusdae and juveniles of Basilichthys microlepidotus were capable of very similar standardized critical swimming speeds of 69.7 and 69.6 cm s^?1, respectively. When expressed in units of body lengths, C. galusdae was capable of very high critical speeds of 16.2 bl s^?1, whereas for B. microlepidotus, this was 7.6 bl s^?1. However, fixed velocity tests revealed that the swimming endurance of the latter species was slightly higher. Dimensionless analysis showed a clear relationship between fatigue time and fish Froude number, similar to that already described for subcarangiforms. Based on these results, we present fishway design curves indicating a transition from sustained to prolonged swimming at a fishway length of 15 m. Our results show that the swimming capacity of these species is well‐suited to the mean flow velocity field described for nature‐like fishways. However, more work is required to understand the effects of turbulence on the passage of non‐sport species. Copyright © 2016 John Wiley & Sons, Ltd.     

Partial dam removal restores passage for a threatened salmonid

Dams represent one of the major forms of river alteration. As these structures reach the end of their lifespan, they often require extensive refurbishments or removal. A small‐scale water supply dam in Banff National Park (Alberta, Canada) was partially removed, creating a breach that allowed water to scour a new passage resembling a nature‐like fishway. We investigated the permeability of the partially removed dam as a means of validating the conservation benefits of the partial dam removal. We quantified the proportion of bull trout (Salvelinus confluentus), a threatened species in Canada, that approached and passed the fishway using radio telemetry receiver stations. The proportion of bull trout that approached the fishway was low (37.0%; N = 27 of 73), but was consistent with upstream reference sites (33%; N = 20 of 60). For those that did approach, the proportion of bull trout that passed yielded a high passage efficiency (77.8%; N = 21 of 27 that approached). The probability that a fish passed the fishway was related to water depth and time of day. Bull trout were more likely to pass when water depths were high (>0.40 m), and at night. Passage duration ranged from 5‐mins to 13‐days, suggesting that this resident species used the fishway for a variety of purposes (e.g., station holding and foraging) and not just transiting. Some individuals underwent large‐scale movements 2‐km upstream (15.1%; N = 11 of 73), or 2‐km downstream (2.7%; N = 2 of 73) following a successful passage event. This study provides new insight on how, in some instances, a breach in a dam can function as a nature‐like fishway, accommodating year‐round stream flows and providing hydraulic conditions suitable for fish passage without costly engineering or construction.     

Fish passage modelling for environmental flows: Hawkesbury‐Nepean River,NSW, Australia

Robust, objective, and repeatable approaches that define flow thresholds for fish passage across critical natural barriers such as riffles, rapids, and waterfalls are required for determining environmental flow strategies. These approaches also provide an opportunity to garner community sector backing for environmental flow releases from dams in support of tangible environmental beneficiaries—native fish. This paper outlines the results of a two‐dimensional hydraulic modelling approach to fish passage assessment for Australian bass (Percalates novemaculeata) that was used to inform the development of an environmental flow regime downstream of Warrragamba Dam, NSW, Australia. Flow rates of ≥500 MLd^?1 were found to facilitate depth‐limited upstream passage through a 20‐km river reach that contained 19 natural passage barriers to adult Australian bass up to 400–450 mm in length. Ideal passage conditions were determined at flow rates of ≥1,000 MLd^?1. Juvenile bass passage was found to be inhibited by high velocities at flow rates >250 MLd^?1, with flows of 100–250 MLd^?1 providing ideal conditions for juvenile passage. Fish length, body depth, and caudal fin depth data, as used in this study for Australian bass, provided more precise fish passage depth thresholds. Precision in fish passage assessments is important as each centimetre of additional flow depth influences cost–benefit analyses of environmental flow releases versus consumptive water uses. Although hydraulic modelling and field‐based approaches to fish passage assessment are well established, there is currently a lack of published data on native Australian freshwater fish length, body depth, and caudal fin depth data for use in fish passage assessments and for inclusion in “fish‐friendly” government policy initiatives.     

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.