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Wild riverine fishes are known to rely on burst swimming to traverse hydraulically challenging reaches, and yet there has been little investigation as to whether swimming anaerobically in areas of high flow can lead to delayed mortality. Using acoustic accelerometer transmitters, we estimated the anaerobic activity of anadromous adult sockeye salmon (Oncorhynchus nerka) in the tailrace of a diversion dam in British Columbia, Canada, and its effects on the remaining 50 km of their fresh-water spawning migration. Consistent with our hypothesis, migrants that elicited burst swimming behaviors in high flows were more likely to succumb to mortality following dam passage. Females swam with more anaerobic effort compared to males, providing a mechanism for the female-biased migration mortality observed in this watershed. Alterations to dam operations prevented the release of hypolimnetic water from an upstream lake, exposing some migrants to supraoptimal, near-lethal water temperatures (i.e., 24°C) that inhibited their ability to locate, enter, and ascend a vertical-slot fishway. Findings from this study have shown delayed post--dam passage survival consequences of high-flow-induced burst swimming in sockeye salmon. We highlight the need for studies to investigate whether dams can impose other carryover effects on wild aquatic animals. [ABSTRACT FROM AUTHOR]

ABSTRACT Delays in the freshwater spawning migrations of anadromous fishes at upstream barriers are well documented, but underlying mechanisms causing slowed migrations are seldom known. Using acoustic accelerometer transmitters and generalized linear models, we investigated how alterations in flow at a diversion dam in British Columbia, Canada, affected the activity, behaviour and passage success of a Fraser River sockeye salmon population ( Oncorhynchus nerka). Spilling excess water through the radial gate of the dam decreased the attraction efficiency of a vertical-slot fishway by 90% and increased delay below the dam by 2 h, which had adverse effects on passage. Relative to males, female sockeye salmon had significantly lower passage success (73% vs 94%), attraction efficiency (79% vs 100%) and passage efficiency (89% vs 94%) at a fishway, delayed longer in the dam tailrace (mean ± standard error (SE): 20·8 ± 4·1 h vs 14·6 ± 3·2 h), and resorted to anaerobic swimming efforts for a greater percentage of time (0-61·3% vs 0·7-2·7%). Given that the persistence of Pacific salmon populations relies on the spawning success of females, understanding how males and females vary in their response to modified flow regimes will improve the management of complex fish-passage problems. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Upstream migration of juvenile stages of temperate Australian amphidromous fish typically coincides with seasonally low river discharge when hydraulic (e.g. cascades) and physical (e.g. rock bars) barriers may be common. The ability to 'climb' or 'jump' may be expected to assist in negotiating low-flow barriers; however, it is presumed to be limited to a few native Australian freshwater fishes. Juvenile stages of Galaxias truttaceus Valenciennes, 1846 were observed 'climbing' and 'jumping' to successfully negotiate a low, vertical weir wall during their upstream recruitment migrations in south-western Australia. Based on this observation, we propose initial definitions for 'climbing' and 'jumping' to describe locomotory strategies employed by fishes to negotiate obstacles that would otherwise prevent free passage by normal swimming behaviour. Greater knowledge of the climbing, jumping and swimming performance, especially for small-bodied species and early life stages, will help improve the management of instream barriers for this critically endangered species and other freshwater fishes of southern Australia. We describe observations of juvenile trout minnow (Galaxias truttaceus) 'climbing' and 'jumping' over a vertical weir wall in south-western Australia. This observation enhances our knowledge of the migratory capability, and therefore long-term management, of this species and highlights the need for a better understanding of the swimming capabilities of freshwater fishes in general. [ABSTRACT FROM AUTHOR]

Construction of instream barriers, preventing fish from accessing spawning, nursery and feeding habitat, is a major issue impacting fisheries sustainability throughout the world. Since European settlement, development in the Murray-Darling Basin for irrigation and potable water supplies has led to the construction of over 10,000 barriers to fish movement. The Native Fish Strategy listed fish passage as a major driving action and was proactive in progressing cost-effective solutions to help inform large-scale rehabilitation programmes. The strategy identified a list of high-priority barriers for mitigation works based on feedback from jurisdictional agencies. Research initiatives were then implemented, with measurable outcomes, to help address key knowledge gaps. Research demonstrated that a project to restore passage to the Murray River main channel was meeting all ecological and engineering objectives. Follow-on work identified low-cost mechanisms to improve the effectiveness of existing fishways without compromising ecological functionality. The Native Fish Strategy was also explicit in addressing fish passage issues at irrigation infrastructure and wetland regulators. Work to minimise these impacts included quantifying the scale of irrigation-associated infrastructure and also optimising screen designs to be retrofitted to pump systems to prevent fish entrainment. Options to enhance lateral movement were also identified. The objective of this study is to summarise the fish passage issues progressed by the Native Fish Strategy to develop basin-wide solutions to enhance fish passage over the long term. [ABSTRACT FROM AUTHOR]

Abstract: The biggest problem involved in installing fishways at obstacles across natural streams is to engineer the optimal position of the fishway entrance. The four criteria that were used in this study to construct a fishway at low-head submerged weirs located in the Han River of Korea are established based on previous studies. The criteria include, the farthest point toward upstream, the vicinity of the thalweg, the vicinity of the primary velocity, and a point of less erosion and deposition. Among these, the third and fourth criteria are revealed by means of flow and sediment transport analysis. In particular, the entrance and exit of a fishway have often been closed due to the action of erosion and deposition resulting from extreme flood events that occur in the monsoon season of Korea. Numerical models of two-dimensional flow and sediment transport are used to reveal the structure of the flow field and characteristics of erosion and deposition. The propriety of location of the fishway is verified based on the four criteria using the numerical simulation at the Gapyeng Stream, which has many fishways. The efficiency of the fishway is evaluated indirectly by monitoring the fish. The criteria are also used to locate the best position of a fishway at a weir located in the Wangsuk Stream, which is a tributary of the Han River and does not have any fishway. [Copyright &y& Elsevier]

This study evaluated the effect of ramp length and slope on fish passage over baffled ramps with 15° and 30° gradients. Three fish species indigenous to New Zealand were tested: the redfin bully Gobiomorphus huttoni, the common bully Gobiomorphus cotidianus and the inanga Galaxias maculatus with ramp lengths of 3, 4·5 and 6 m. As slope and ramp length increased, passage success rate decreased for G. maculatus and G. cotidianus. At a slope of 15°, both G. maculatus and G. cotidianus could pass all ramp lengths tested with the highest success rate on the 3 m ramp. As the gradient increased to 30°, G. maculatus could only pass the 3 m ramp, and G. cotidianus were incapable of passing any ramp. Gobiomorphus huttoni were the only test species capable of climbing the wetted margin of the ramps. Increasing ramp slope significantly reduced passage success for G. huttoni, but ramp length, up to the maximum used in this study, had no significant influence on successful passage. [ABSTRACT FROM AUTHOR]

We synthesized evidence for unintended consequences and trade-offs associated with the passage of fishes. Provisioning of fish passageways at dams and dam removals are being carried out increasingly as resource managers seek ways to reduce fragmentation of migratory fish populations and restore biodiversity and nature-like ecosystem services in tributaries altered by dams. The benefits of provisioning upstream passage are highlighted widely. Possible unwanted consequences and trade-offs of upstream passage are coming to light, but remain poorly examined and underappreciated. Unintended consequences arise when passage of native and desirable introduced fishes is delayed, undone (fallback), results in patterns of movement and habitat use that reduce Darwinian fitness (e.g. ecological traps), or is highly selective taxonomically and numerically. Trade-offs arise when passage decisions intended to benefit native species interfere with management decisions intended to control the unwanted spread of non-native fishes and aquatic invertebrates, or genes, diseases and contaminants carried by hatchery and wild fishes. These consequences and trade-offs will vary in importance from system to system and can result in large economic and environmental costs. For some river systems, decisions about how to manage fish passage involve substantial risks and could benefit from use of a formal, structured process that allows transparent, objective and, where possible, quantitative evaluation of these risks. Such a process can also facilitate the design of an adaptive framework that provides valuable insights into future decisions. [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]

Few studies have been conducted to evaluate the effectiveness of nature-like fishways, particularly in low gradient warmwater streams with diverse fish communities. We evaluated a nature-like fishway that was installed to facilitate upstream passage at a low head dam on Indian Creek near Spencerville, Ontario, Canada. A passive integrated transponder ( PIT) array was used to quantify attraction and passage efficiency for 391 PIT tagged warmwater fish, represented by seven species. Attraction efficiency for the three most common species, common shiner ( Luxilus cornutus), creek chub ( Semotilus atromaculatus) and white sucker ( Catostomus commersonii), was 63.3%, 83.7% and 65.6%, respectively, and passage efficiencies were 5.1%, 38.4% and 25%, respectively. Creek chub were able to locate the fishway in less time than white sucker and common shiner; however, took longer to successfully pass. Manipulation of creek chub release locations was used to separate issues of attraction and passage and revealed that passage efficiency was highest (76.2%) for those released within the fishway and intermediate for those released at the entrance (42.1%). This multispecies fishway improved stream connectivity, but additional work is needed to fine tune its configuration. Similar projects that engage stakeholders in nature-like fishway construction are a promising approach for the thousands of small dams that occur on low gradient streams around the globe, but those studies should incorporate a biological evaluation to ensure that attraction and passage efficiency are optimised. [ABSTRACT FROM AUTHOR]

ABSTRACT A shift from target species to ecosystem restoration has generated interest in developing fishways that are capable of passing entire fish communities. Although a number of multispecies fishways now exist in North America, evaluations of these fishways are lacking. We used a passive integrated transponder antenna array to quantify passage success and passage duration of fish using a vertical slot fishway (85 m in length, 2.65 m elevation rise, 12 regular pools and 2 turning basins) at a low head dam on the Richelieu River in Quebec, Canada. Fourteen of the 18 tagged species re-ascended the fishway, and passage efficiency was highly variable among species (range 25%-100%); however, it was >50% for five of the species well represented in this study ( n > 10) (Atlantic salmon, channel catfish, smallmouth bass, walleye and white sucker). Passage duration was likewise highly variable both among and within species (e.g. 1.0-452.9 h for smallmouth bass, 2.4-237.5 h for shorthead redhorse). Although this fishway design was not uniformly successful in passing fish of all species, this study does reveal the species that have problems with ascent and provides an estimate on the time spent in the fishway that is an important component of passage delay. Such information could be used to inform future design refinements to facilitate passage of the entire assemblage with minimal delay. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A river fishway is a hydraulic structure enabling fish to overcome stream obstructions such as dams in hydroelectric power plants. The main aim of this paper is to present an application of mathematical modeling and optimal control theory to an ecological engineering problem related to preserve and enhance natural stocks of fish migrating between saltwater and freshwater. Particularly, we improve the optimal shape design of a fishway. This problem is formulated within the framework of the optimal control of partial differential equations, approximated by a discrete optimization problem, and solved by using both a gradient method (a Spectral Projected-Gradient algorithm) and a derivative-free method (the Nelder-Mead algorithm). Finally, numerical results are compared and analyzed for a standard real-world situation. [ABSTRACT FROM AUTHOR]

Low dam passage rates of adult Pacific lamprey ( Entosphenus tridentatus) during upstream spawning migration have been implicated in the species' steep decline in the interior Columbia River basin. In this 2000-2010 study, we used radiotelemetry to evaluate potential predictors of lamprey passage success at McNary Dam, located ~469 river kilometres (rkm) from the Pacific Ocean. The tagged population included 276 lampreys collected at McNary Dam and 53 collected at Bonneville Dam (rkm 235) that migrated to McNary Dam. McNary Dam passage efficiency was similar for the two samples, with multiyear estimates of 0.65 and 0.75, respectively. Larger-bodied lampreys and those with earlier migration timing were more likely to return to McNary Dam after release, to pass the dam and to be detected upstream from McNary reservoir. Far more lampreys entered the upper Columbia River than the Snake River, suggesting that environmental cues (e.g., water discharge, temperature) or conspecific cues (e.g., pheromone concentrations) affect lamprey distribution above this large confluence. Overall, results indicate that Pacific lamprey passage success at barriers depends on a combination of individual lamprey traits plus seasonal and site-specific effects on behaviour. [ABSTRACT FROM AUTHOR]

Abstract: Fish passage systems may provide a means to mitigate the barrier effect of dams on migrating fish species. Even though design criteria were initially developed for the fish fauna of temperate regions, they are widely used in tropical rivers with relative success. A fish passage concept has been developed for a hydroelectric power project on the Mekong River in the absence of suitable fish passage design criteria. There are several hydropower dams proposed for development on the mainstem of the Mekong River in Cambodia, Laos, Thailand and China and the impact of hydropower on fisheries is fast becoming a big issue. Located in Laos territory, the present project is one of the promising run-of-river hydropower projects identified by the Mekong Secretariat in 1994. The feasibility study began in 2007 and the outline (basic) design is being completed in 2010. The scheme includes a comprehensive fish passage system, which provides facilities for upstream and downstream passage. The proposed fish passage concept is based on twelve principles and gives emphasis on an adaptive project management, which includes planning, implementation and operation of the fish passage system and other structures of the project. It will cater to the large number of species and high biomass and especially to the variable flow regime and the lack of biological knowledge on the behavior of migrating species. [Copyright &y& Elsevier]

While dams cut off the migratory route of fish, and affect their growth and breeding, fishways are built to restore the connectivity of rivers and facilitate the life cycle of these migratory fish. This paper proposes a new kind of fishway called the “T shape fishway”, and studies it by using both numerical simulations and physical experimental methods with the aim to design a fishway in China for migratory fish with swimming and jumping capability much poorer, such as schizothorax davidi and schizothorax prenanti, as compared with migratory fish in other places of the world, like trout and salmon. It is indicated that the range of velocity in each regular pool of the T shape fishway is from 0.42 m/s to 1.22 m/s when the flow discharge Q is 350 L/s, and there are no large vortex zones found there. This study shows that the T shape fishway can meet the requirements of these migratory fish quite well in terms of velocity and flow patterns in China. [ABSTRACT FROM AUTHOR]

Schizothorax chongi (locally known as Xilian Yu), a fish species commonly found in Yalong River, has been declining quickly in recent years. One of the important factors, among many, is the interruption of the free flowing river by dams. To obtain data that can be applied to the design of a fishway for S. chongi and other species in the community, a laboratory study of juvenile S. chongi's swimming energetics and kinematics was conducted in a flume-type respirometer equipped with a high speed video camera system to record swimming behavior. The aerobic metabolic rate, tail beat frequency (TBF) and tail beat amplitude (TBA) were measured during steady swimming at varying flow rates for fish of similar mass. A power function accurately describes the relationship between oxygen consumption rate (MO) and swimming speed ( U). The estimated standard metabolic rate (SMR) calculated from the power function was 445.34 mg O kg h, similar to the experimental result of 431.5 mg O kg h. The relationship between cost of transport (COT) and U was, characteristically, inverse bell-shaped, with COT = 44.6 J kg m at U = 5.5 body lengths per second (bl s). There was a significant positive linear correlation between TBF and U. The slope of the correlation (0.33) was lower than for many other species, implying that S. chongi swim efficiently. The TBA, ranging from 0.15 to 0.2 bl, was found to be independent of U. Kinematic analyses indicates that S. chongi primarily depends on the caudal fin to generate forward thrust and employs three velocity-dependent swimming gaits. This investigation provides data on the swimming ability of S. chongi that will add to the basic science required for fishway design. [ABSTRACT FROM AUTHOR]

The movements of 28 adult chum salmon, Oncorhynchus keta (Walbaum) tagged with electromyogram (EMG) transmitters were tracked along the Toyohira river, Hokkaido, Japan, in October of 2007 and 2008 to investigate and evaluate the upstream migratory behavior through the protection bed and fishway of ground sills. The approach time of fish that ascended successfully through the protection bed and fishway was shorter than that of unsuccessful fish. The unsuccessful fish were observed to swim in currents with high water velocity and shallow water depth at swimming speeds that exceeded their critical swimming speed ( U) during the approach to these structures. In consequence, unsuccessful fish frequently alternated between burst and maximum sustained speeds without ever ascending the fishway, and eventually became exhausted. It is important that fishway are constructed to enable chum salmon to find a passage way easily, so that they can migrate upstream rapidly without wasting excessive energy. [ABSTRACT FROM AUTHOR]

Fishways and other passage facilities frequently prevent or delay the passage of fishes, highlighting the need for effectiveness monitoring. We reviewed the scientific literature from 1960 to 2008 reporting on effectiveness monitoring of fish passage facilities to assess what taxa and life-stages have been studied, the questions that are asked during evaluation, and how these varied over time or by geographic region. We identified 96 peer-reviewed articles of which 68% focused on passage by adult fishes. Salmoniformes was the most studied order (58% of studies). The focus of fishway evaluations did not change over the years, but varied significantly by geographic region. Studies from the tropics had a broader taxonomic scope than studies from temperate locations. Exogenous mechanisms of passage failure, such as environmental, structural and behavioural factors, were studied in 90% of studies from North America but only ∼50% of studies from Europe, South America and Australia. Endogenous (i.e. physiological) mechanisms affecting passage success were not often assessed anywhere, though they were a powerful means of evaluating mechanisms of failure. Few studies monitored migration after fish had left a facility. To improve effectiveness monitoring of passage facilities, we suggest that both endogenous and exogenous mechanisms need to be studied in an integrated fashion to understand passage failure and to inform design or operational changes that could improve passage efficiency. In addition post-departure monitoring is required to more completely assess the fitness consequences of passage. [ABSTRACT FROM AUTHOR]

Simple Summary: A lack of information on fish volitional swimming behavior in response to various instream flow conditions may inhibit the development of an effective fishway. In this study, Schizothorax prenanti, Tchang, 1930 (S. prenanti), an endemic species in the Jinsha river basin, was tested for volitional swimming behavior in a self-designed open-channel flume. Quantified indices, describing preferred hydraulic characteristics, swimming strategies, and swimming speeds, were collected to analyze fish behavioral responses to turbulent flow. The results showed that S. prenanti preferred to select regions with low flow velocities (0.25–0.50 m/s) and turbulent kinetic energy (<0.05 m2/s2) and employed steady swimming behavior to search for flow velocities lower than the average current to conserve energy in low- and moderate-flow regimes. Additionally, the average and maximum burst speeds of S. prenanti were 2.63 ± 0.37 and 3.49 m/s, respectively. The aim of this study was to apply fish volitional swimming behavior data on the the design and optimization of fishways for specific target species, as well as a novel test method for other migratory fish species. Effective fishway design requires knowledge of fish swimming behavior in streams and channels. Appropriate tests with near-natural flow conditions are required to assess the interaction between fish behavior and turbulent flows. In this study, the volitional swimming behavior of S. prenanti was tested and quantified in an open-channel flume with three (low, moderate, and high) flow regimes. The results showed that, when confronted with alternative flow regimes, S. prenanti preferred to select regions with low flow velocities (0.25–0.50 m/s) and turbulent kinetic energy (<0.05 m2/s2) for swimming, while avoiding high-turbulence areas. Moreover, S. prenanti primarily employed steady swimming behavior to search for flow velocities lower than the average current to conserve energy in low- and moderate-flow regimes. It is hypothesized that in regions with higher flow velocities, fish may change their swimming strategy from energy conservation to time conservation. Additionally, the average and maximum burst speeds of S. prenanti were 2.63 ± 0.37 and 3.49 m/s, respectively, which were 2.21- and 2.28-fold higher than the average (1.19 m/s) and maximum (1.53 m/s) burst speeds estimated from the enclosed swim chamber for fish of similar length. This study contributes a novel research approach that provides more reliable information about fish volitional swimming behavior in natural habitats, as well as recommendations for hydraulic criteria for fishways and the identification of barriers to fish migrations. [ABSTRACT FROM AUTHOR]

Large-scale migratory patterns of adult rheophilic fish [barbel, Barbus barbus (L.), chub, Leuciscus cephalus (L.), ide, Leuciscus idus (L.), nase, Chondrostoma nasus (L.)] were studied in relation to habitat quality and possible migration barriers in the lower rivers Meuse and Rhine, the Netherlands, using a telemetry system with transponders and detection stations based on inductive coupling. Most fish moved over short distances (<10 km), especially those residing in river stretches with high habitat diversity year-round. About 16% of fish used river stretches over 50 km and two ide moved more than 200 km along free-flowing river stretches. One-third of barbel, chub and nase from a Weir-regulated river stretch moved upstream during the spawning season to spawning habitats. Some fish resided in the areas immediately downstream of weirs and fishways during the spawning season, although it was unclear to what extent these observations reflected habitat choice or barriers to migration. [ABSTRACT FROM AUTHOR]

The investigations presented here were carried out at the Technical University of Dresden and the University of Stuttgart in order to optimize the current method for the design of fish passage structures with perturbation boulders. However, in the course of the analyses it was found that the specifications of the relevant German code of practice, DVWK Bulletin 232, did not take adequate account of the leading-edge flow conditions and that there were, in parts, considerable discrepancies between the calculated and the measured values. For this reason, a modified computational approach has been derived theoretically and verified on the basis of model tests. Furthermore, a method has been developed for dimensioning these structures that has already been implemented on the first facilities. [ABSTRACT FROM AUTHOR]

Several vertical slot fishways have been built in France over the last 20 years. This type of pool fish pass is generally very effective in ensuring passage of the target species, particularly diadromous species. However, visual observations have shown that certain small species may be trapped in the large recirculation zones and seem to have difficulty in rapidly passing through very large pools. An experimental study was undertaken to characterize the turbulent flow for various configurations of vertical slot fishways and to determine how they might be modified to facilitate the passage of small species. The characteristics of mean flow and turbulence were studied by particle image velocimetry (PIV) for three slopes ( I = 5%, 10%, 15%), three flow discharges ( Q = 576, 736, 864 L/s) and four pool widths ( B = 1.7, 2, 2.3, 2.7 m). The results showed that the flow pattern always follows one of two topological models depending on the length/width ratio of the pool. A strong link was found between the calculated volumetric dissipated power and the mean kinetic energy of velocity fluctuations measured in the pools. In order to study the extent to which the dimensions of recirculation zones can be reduced, the effect of the insertion of vertical cylinders within the pools was displayed by laser tomography. [ABSTRACT FROM AUTHOR]

Fish passage structures are built to restore the connectivity of rivers and allow the migration of aquatic fauna. In order to assess the functioning of a pool-type fishway, it is necessary, inter alia, to possess detailed knowledge of its flow structure, since observations of fishways, and in particular of the visible water surface, can only provide a rough idea of the actual conditions inside the pools. Numerical simulation has been used for many years to support engineering sciences. Especially, the modeling of flow processes in hydraulic machines can, on the one hand, help avoid major problems during the design stage of fish passage structures and, on the other, improve the structure’s hydraulic performance. To this end, two diploma theses within the framework of a research project of the local energy supplier Energie Baden-Württemberg AG (EnBW) employed modeling tools for 3D flow simulation, primarily for pool-slot fishways (PSF), and for traditional vertical slot fishways (VSF). [ABSTRACT FROM AUTHOR]

Abstract: A river fishway is a hydraulic structure that facilitates fish in overcoming obstacles (dams, waterfalls, etc.) to their spawning and other migrations in rivers. In this work we present a mathematical formulation of an optimal design problem for a vertical slot fishway, where the state system is given by the 2D shallow water equations fixing the height and velocity of water, the design variables are the geometry of the slots, and the objective function is determined by the existence of rest areas for fish and of a water velocity suitable for fish swimming capability. We also derive an expression for the gradient of the objective function via the adjoint system. From the numerical point of view, we present a characteristic-Galerkin method for solving the shallow water equations, and a direct search algorithm for the computation of the optimal design variables. Finally, we give numerical results obtained for a standard ten pools channel. [Copyright &y& Elsevier]

The diel variation in boat electrofishing catches was investigated on the lower Murray River (south-eastern Australia), downstream of three low-level weirs. Fish assemblage composition did not differ among three sites, but differed substantially between day and night. Significantly more small-bodied species ( e.g. Australian smelt Retropinna semoni, flyspecked hardyhead Craterocephalus stercusmuscarum, bony herring Nematalosa erebi and Murray rainbowfish Melanotaenia fluviatilis) and some large-bodied predators ( e.g. golden perch Macquaria ambigua) were caught during daytime samples. Significantly more flatheaded gudgeon Phylipnodon grandiceps, carp gudgeon Hypseleotris spp. and perch Perca fluviatilis were collected at night. The size composition of the fish assemblage also changed over the diel cycle. Significantly smaller goldfish Carassius auratus, flyspecked hardyhead, bony herring and Australian smelt were sampled during the day, while generally smaller individuals of golden perch and the common carp Cyprinus carpio were caught at night. These findings suggest that sampling during both day and night is required to adequately characterize riverine fish assemblages in the context of fish migration studies. [ABSTRACT FROM AUTHOR]

Abstract: This paper provides a rigorous and directed research framework for fostering innovations in the design, implementation, and operation of barriers, traps, and fishways used to control the sea lamprey (Petromyzon marinus) in the Laurentian Great Lakes. It was developed to support the Great Lakes Fishery Commission''s milestone pledging to decrease reliance on chemical lampricides and achieve 50% of sea lamprey suppression through alternative control technologies, including barriers and traps. The paper first substantiates the need to develop a long-term research plan for barriers, traps, and fishways by summarizing (i) current management challenges, (ii) the barrier, trap, and fishway options being used to meet these challenges, and (iii) the key uncertainties in our knowledge regarding these options. The paper then proposes a long-term research strategy that envisions a transition from barriers designed to block the upstream spawning migrations of sea lamprey, to barrier and trap combinations that facilitate physical removal of sea lamprey and, in some cases, passage of non-target fishes, to barrier and trap designs that are specific to sea lamprey, transparent to non-target fishes, and safer for operators. Thirteen research needs are identified to support this strategy along with a general work plan on how they can be achieved. The research needs and work plan highlight the exceptional opportunity to develop the Great Lakes basin as a leading, international research center for fish migration and passage, and the development of environmentally friendly barriers. [Copyright &y& Elsevier]

Abstract: One of the major problems in fishway design is that optimal parameters depend on an interplay of hydraulic and biological variables. This study presents a methodology for evaluating fishway designs in terms of the swimming capabilities of the target species. Specifically, we have evaluated two vertical-slot designs whose hydraulic properties were empirically characterized in a previous study. In view of these empirical data, for each design we have estimated (a) minimum discharges giving minimum fish-acceptable depths; (b) maximum pool sizes ensuring flow velocities low enough to be overcome by the fish; (c) maximum pool sizes ensuring turbulence low enough to be acceptable to the fish. These design constraints are calculated for different slopes (∼6 or ∼10%), different water temperatures (10, 15 or 20°C), and different fish lengths. This methodology constitutes an effective means of taking fish swimming capabilities into account at the fishway design stage. [Copyright &y& Elsevier]

Wild Alaskan sockeye salmon Oncorhynchus nerka jumping natural waterfalls were observed and photographed to obtain insight into factors important to the fish in dealing with obstacles during their upstream spawning migrations. The fish showed preferences for specific sets of conditions related to heights of waterfalls and depths in pools below waterfalls. Successful jumps appeared to result from running starts, not standing fast starts. The proportion of observed jumps that were successful was low (10% at Brooks Falls, Katmai National Park, Alaska, U.S.A.). Successful jumping behaviour was modelled mathematically and predictions were compared to measured kinematic variables of successful and unsuccessful jumping obtained from analyses of digital video photographs. There were statistically significant differences between the two data sets, but the model identified takeoff velocities and angles, and distances between takeoffs and successful landings as important variables. [ABSTRACT FROM AUTHOR]

Migrating fish traversing velocity barriers are often forced to swim at speeds greater than their maximum sustained speed (Ums). Failure to select an appropriate swim speed under these conditions can prevent fish from successfully negotiating otherwise passable barriers. I propose a new model of a distance-maximizing strategy for fishes traversing velocity barriers, derived from the relationships between swim speed and fatigue time in both prolonged and sprint modes. The model predicts that fish will maximize traversed distance by swimming at a constant groundspeed against a range of flow velocities, and this groundspeed is equal to the negative inverse of the slope of the swim speed-fatigue time relationship for each mode. At a predictable flow velocity, they should switch from the optimal groundspeed for prolonged mode to that for sprint mode. Data from six migratory fish species (anadromous clupeids: American shad Alosa sapidissima, alewife A. pseudoharengus and blueback herring A. aestivalis; amphidromous: striped bass Morone saxatilis; and potomodromous species: walleye (previously known as Stizostedion vitrium) and white sucker Catostomus commersonii) were used to explore the ability of fish to approximate the predicted distance-maximizing behaviors, as well as the consequences of deviating from the optima. Fish volitionally sprinted up an open-channel flume against fixed flow velocities of 1.5-4.5 m s-1, providing data on swim speeds and fatigue times, as well as their groundspeeds. Only anadromous clupeids selected the appropriate distance-maximizing groundspeed at both prolonged and sprint modes. The other three species maintained groundspeeds appropriate to the prolonged mode, even when they should have switched to the sprint optima. Because of this, these species failed to maximize distance of ascent. The observed behavioral variability has important implications both for distributional limits and fishway design. [ABSTRACT FROM AUTHOR]

The improvement of the weir without a fishway is required in order that diadromous fishes, shrimps, and crabs can migrate to their upstream and downstream habitats. This paper presents a proposal of a portable fishway to be set on the waterside of a trapezoidal weir and discusses the effect of the proposed fishway on the migration of diadromous aquatic animals in the trapezoidal weir. Field experiments concerning the proposed fishway were carried out at a trapezoidal weir having a slope of 26.5° (Vertical 1: Horizontal 2) and 2.0 m drop height. The field experiments revealed that the juvenile ayu fish (Plecoglossus altivelis) having a body length of 4.4–10 cm could migrate to their upstream habitats through the proposed portable fishway even if the slope of the fishway is 19°. About 120 000 juvenile ayu could migrate upstream via the fishway during 9 d. The migration route of juvenile ayu can be explained on the basis of the flow characteristics in the fishway. Measurements of the flow velocity and the air concentration distribution in the portable fishway support the conclusion that the juvenile ayu can easily migrate upstream through the fishway. Also, the proposed fishway could be helpful for the upstream migration of benthic fishes, shrimps, and crabs. [ABSTRACT FROM AUTHOR]

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., Competing Interests: The authors declare no conflict of interest.

A river is an ecosystem where fish fauna represents an important structural element. To re-establish connectivity, it is imperative to allow movement between functional habitats. Due to the hydromorphological complexity of large anthropized rivers and the lack of study techniques that can be used in such environments, relevant data with regard to fish ecology are scarce. On the River Meuse, Belgium, at a point 323 km upstream from the North Sea, the Lixhe hydroelectric dam is equipped with two fishways. Both were continuously monitored using capture traps for 20 consecutive years (from 1999 to 2018), representing 4151 monitoring events. The objectives of the present study were to describe the overall abundance and movement indicators of mainly holobiotic potamodromous fish species and to analyse their temporal evolution. We captured 388,631 individuals (n = 35 fish species) during the 20 years of fishway monitoring; 22.7% were adults (>75% of which were cyprinids), and 83.3% juveniles (>90% cyprinids). From 1999 to 2018, the results showed a drastic reduction in yearly captures for some native species as well as the apparent emergence of non-native (e.g., Silurus glanis) and reintroduced species (e.g., Salmo salar). The annual capture periodicities associated with environmental factors were clearly defined and were mostly related to the spring spawning migration of the adult stage. This long-term monitoring demonstrated how the fishways are used by the whole fish community and allowed a better understanding of their movement ecology in a large lowland anthropized river. The appearance of non-native species and the drastic decline in abundance of some common and widespread European fish should prompt river managers to adopt conservation measures. [ABSTRACT FROM AUTHOR]

Biological invasions are poorly controlled and contribute to the loss of ecosystem services and function. Altered watershed connectivity contributes to aquatic invasions, but such hydrologic connections have become important for human transport. Carbon dioxide (CO 2 ) deterrents have been proposed to control the range expansion of invasive fishes, particularly through altered hydrologic connections, without impeding human transport. However, the effectiveness of CO 2 deterrents needs to be further evaluated in the field, where fishes are situated in their natural environment and logistical challenges are present. We deployed a proof-of-concept CO 2 deterrent within a trap-and-sort fishway in Cootes Paradise, Ontario, Canada, to determine the avoidance responses of fishes attempting to disperse into a wetland. We aimed to describe deterrent efficiency for our target species, common carp, and for native fishes dispersing into the wetland. Our inexpensive inline CO 2 deterrent was deployed quickly and rapidly produced a CO 2 plume of 60 mg/l. Over 2000 fishes, representing 13 species, were captured between 23 May and 8 July 2019. A generalized linear model determined that the catch rates of our target species, common carp ( n  = 1662), decreased significantly during deterrent activation, with catch rates falling from 2.56 to 0.26 individuals per hour. Aggregated catch rates for low-abundance species ( n  < 150 individuals per species) also decreased, while catch rates for non-target brown bullhead ( n  = 294) increased. Species did not express a phylogenetic signal in avoidance responses. These results indicate that CO 2 deterrents produce a robust common carp avoidance response in the field. This pilot study deployed an inexpensive and rapidly operating deterrent, but to be a reliable management tool, permanent deterrents would need to produce a more concentrated CO 2 plume with greater infrastructural support., (© The Author(s) 2022. Published by Oxford University Press and the Society for Experimental Biology.)

Effective fishway design requires knowledge of fish swimming behavior in streams and channels. Appropriate tests with near-natural flow conditions are required to assess the interaction between fish behavior and turbulent flows. In this study, the volitional swimming behavior of S. prenanti was tested and quantified in an open-channel flume with three (low, moderate, and high) flow regimes. The results showed that, when confronted with alternative flow regimes, S. prenanti preferred to select regions with low flow velocities (0.25−0.50 m/s) and turbulent kinetic energy (<0.05 m2/s2) for swimming, while avoiding high-turbulence areas. Moreover, S. prenanti primarily employed steady swimming behavior to search for flow velocities lower than the average current to conserve energy in low- and moderate-flow regimes. It is hypothesized that in regions with higher flow velocities, fish may change their swimming strategy from energy conservation to time conservation. Additionally, the average and maximum burst speeds of S. prenanti were 2.63 ± 0.37 and 3.49 m/s, respectively, which were 2.21- and 2.28-fold higher than the average (1.19 m/s) and maximum (1.53 m/s) burst speeds estimated from the enclosed swim chamber for fish of similar length. This study contributes a novel research approach that provides more reliable information about fish volitional swimming behavior in natural habitats, as well as recommendations for hydraulic criteria for fishways and the identification of barriers to fish migrations.

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]