Fish Passage Research Articles

NEW DESIGNS OF FISH-PASSING FACILITIES

The paper deals with the research of new structures of concrete hydraulic structures. An important stage in their design is the correct choice of groups of fish passage structures. It is worth noting that the selection of the structure group is carried out mainly on the basis of technical and economic comparisons, and not for structural reasons, taking into account the possibility of fish passing along the entire length of the tract.

Balancing renewable energy and river resources by moving from individual assessments of hydropower projects to energy system planning

As governments and non-state actors strive to minimize global warming, a primary strategy is the decarbonization of power systems which will require a massive increase in renewable electricity generation. Leading energy agencies forecast a doubling of global hydropower capacity as part of that necessary expansion of renewables. While hydropower provides generally low-carbon generation and can integrate variable renewables, such as wind and solar, into electrical grids, hydropower dams are one of the primary reasons that only one-third of the world’s major rivers remain free-flowing. This loss of free-flowing rivers has contributed to dramatic declines of migratory fish and sediment delivery to agriculturally productive deltas. Further, the reservoirs behind dams have displaced tens of millions of people. Thus, hydropower challenges the world’s efforts to meet climate targets while simultaneously achieving other Sustainable Development Goals. In this paper, we explore strategies to achieve the needed renewable energy expansion while sustaining the diverse social and environmental benefits of rivers. These strategies can be implemented at scales ranging from the individual project (environmental flows, fish passage and other site-level mitigation) to hydropower cascades to river basins and regional electrical power systems. While we review evidence that project-level management and mitigation can reduce environmental and social costs, we posit that the most effective scale for finding balanced solutions occurs at the scale of power systems. We further hypothesize that the pursuit of solutions at the system scale can also provide benefits for investors, developers and governments; evidence of benefits to these actors will be necessary for achieving broad uptake of the approaches described in this paper. We test this hypothesis through cases from Chile and Uganda that demonstrate the potential for system-scale power planning to allow countries to meet low-carbon energy targets with power systems that avoid damming high priority rivers (e.g., those that would cause conflicts with other social and environmental benefits) for a similar system cost as status quo approaches. We also show that, through reduction of risk and potential conflict, strategic planning of hydropower site selection can improve financial performance for investors and developers, with a case study from Colombia.

Bigger than expected: Species- and size-specific passage of fish through hydropower screens

Mitigating the adverse ecological impacts on stream ecosystems caused by hydropower expansion is a major challenge. To prevent fish from turbine entrainment and to reduce injury and mortality risk, physical barriers such as fine screens with horizontally or vertically oriented bars are frequently installed at turbine inlets. In this study, the species- and size-dependent protection from turbine entrainment of different types of fish protection screens (FPSs) were investigated at five hydropower sites by a net-based monitoring of downstream moving wild fish and hatchery-reared test fish during different seasons (15,223 individuals from 40 species). Across different screen types and fish species, considerably larger individuals were able to pass the FPSs than what would have been expected from common models estimating the physical passability of these mechanical barriers. The examined FPSs with 15 mm and 20 mm bar spacing could be passed by adult barbel (Barbus barbus L.), brown trout (Salmo trutta L.) and European perch (Perca fluviatilis L.) up to a total length (TL) of 32 cm (15 mm FPSs) and 34 cm (20 mm FPSs), respectively. In addition, the 20 mm FPSs could be passed by Danube salmon (Hucho hucho L.) up to 39 cm TL. Consequently, thresholds from modelling and rules of thumb for estimating maximum TLs capable of passing 15 mm and 20 mm FPSs were exceeded by up to 135% for these species. The results of this study suggest that fish species other than eel can also squeeze through physical barriers narrower than body dimensions. No physical fish protection was realised by the investigated 15 mm and 20 mm FPSs for many small-bodied species such as bullhead (Cottus gobio L.), gudgeon (Gobio gobio L.) and spirlin (Alburnoides bipunctatus Bloch) with maximum TLs smaller than 20 cm. This also holds true for juveniles and sub-adults of larger species, which can pass these physical barriers. Since a large part of the downstream moving fish generally consists of small species or small individuals, these fish sizes must be given greater consideration in physical fish protection concepts at hydropower plants.

НАУЧНО-ТЕХНИЧЕСКОЕ ОБОСНОВАНИЕ СОЗДАНИЯ ПРИГИДРОУЗЛОВЫХ РЫБОХОДНЫХ, РЫБОХОДНО-НЕРЕСТОВЫХ И НЕРЕСТОВЫХ КАНАЛОВ НА Р. ДОН

Purpose: development of a scientific and technical substantiation for the feasibility of construction and technical solutions for fish pass, fish passage and spawning and spawning channels at waterworks. Materials and methods. The empirical basis of the work was the data of the author's surveys and studies of fish passage and fish-passage and spawning channels operating as part of low-head waterworks on the Western Manych and Don rivers, as well as materials and information on the technical substantiation of the projects of the Bagaevsky and Kochetovsky fish-spawning channels. Results and discussion. In the course of achieving the goal and solving the problems of the study, interpretations of special terms were given: fish passage, fish passage and spawning and spawning channels at the waterworks, and the conditions for the use of each of these structures were formulated. The data of field surveys of the Ust-Manych fish passages and the Konstantinovsky fish passage and spawning channels, carried out in 2022, are presented. Schematic diagrams for the construction of waterworks fish passes, fish passages and spawning and spawning channels are proposed, which, with appropriate study, can be adapted to the specific conditions of their creation and function, which is clearly illustrated by the given examples of design solutions for fish passage and spawning channels arranged as part of the Bagaevsky and Kochetovsky waterworks on the river Don. Structural schemes of facilities and elements that ensure the operation of fish pass, fish passages and spawning and spawning channels, including their main components – tracts, inlet and outlet (for fish) overheads (areas) have been developed. Conclusions. The definitions of the special terms: fish passes, fish passage and spawning (spawning and fish passage) and spawning channels are formulated, and the substantiation of the conditions for their use is given. Layout and structural diagrams for the arrangement of fish passage and fish-passage-spawning channels as part of river low-head waterworks are proposed.

ОБ ОЦЕНКЕ КАЧЕСТВА УСЛОВИЙ ДЛЯ ПРИВЛЕЧЕНИЯ РЫБ В ПРИГИДРОУЗЛОВЫЕ РЫБОХОДНЫЕ И РЫБОХОДНО-НЕРЕСТОВЫЕ КАНАЛЫ

Purpose: to develop a methodology for predicting the quality of design solutions for waterworks fish passages and fish passages and spawning channels for the formation of conditions for attracting fish migrating for spawning into their channels. Materials and methods. The development was based on the results of experimental studies carried out on a hydraulic model of the spillway using small (“model”) fish. When setting up the experiment, the proven methods were used, and when processing experimental data, methods of mathematical statistics were used. Results and discussion. The data of experimental studies of the model fish approach to the entrance sections of fish passages under various hydrometric conditions in the zones of their movement and the size of the spillway have been obtained. The hydrometric factors that influence the attraction of fish from the waterworks downstream to the operation zone of the flow that attracts them and to the entrance to the fish pass are determined: flow rates and average flow velocity in the river and channel, width of the channel and river, attracting and cruising swimming speeds of fish, remoteness of the entrance (for fish) range of the channel from the upper boundary of the fish search area and its length. The qualitative characteristics of the influence of these factors on fish entry and the quantitative values of the degree of their influence on the attraction of fish to the entrances to fish passages have been established. Dependences were obtained. The dependences were tested in the calculation of the fish protection complex of the Bagaevsky waterworks, the efficiency of which (at a spillway discharge of 250 m³/s) is predicted at the level of 92.6 % of the number of fish approaching it. Conclusion. A mathematical model is proposed to determine the value of the quality index of hydrometric conditions in the downstream of the hydroelectric complex to attract fish to the entrance to the fish passage channel, which is a criterion for the quality of its design solution.

Современное состояние и условия функционирования Усть-Манычских рыбоходных каналов

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

Řeka Ohře ve světle vědeckých a praktických rybářských aktivit Antonína Friče realizovaných v rámci záchranné akce na zvýšení populace lososa obecného (Salmo salar) v řekách na území Čech v poslední třetině 19. století

The present study addresses the previously neglected activities of Professor Dr Antonín Frič (1832–1913) from the Museum of the Kingdom of Bohemia (now the National Museum, Prague), realised for the purposes of fisheries development as part of the protective actions in the 1870s through the 1890s to increase the population of the Atlantic salmon (Salmo salar) in Czech rivers. Primary attention is devoted here to Frič’s interest in the Ohře River and its tributaries, which became a major focus for him in the 1880s. Migration of fish into the Ohře, then faced with significant pollution, had been blocked for over a century thanks to the construction of the fortress in Terezín in 1780–1790. A significant event in this respect was the creation of two fish ladders, then still unique in Bohemia, installed in 1885 and 1887 on the strategic weir below the fortress bridge across the New Ohře. Mention is made of Antonín Frič’s achievements in founding fishing associations (Louny, Karlovy Vary, Žatec) and their mutually enriching cooperation. The text is derived primarily from the research results published by Frič and his colleagues in the journal Vesmír and in book form, as well as the study of Frič’s correspondence (Archive of the National Museum, Literary Archive of the National Literary Monument), historic museum catalogues, and Frič’s personal fisheries collections (zoology department of the Museum of Natural Sciences, National Museum, Prague).

Evaluation of a fine-spaced angled rack with surface bypass in providing safe and timely downstream passage for salmon smolts and silver eels

Hydropower production can cause migration delay and fish mortality, impeding the safe and timely downstream migration of diadromous fish, such as Atlantic salmon (Salmo salar) and silver eels (Anguilla anguilla). To date, only a few field performance tests, especially for eels, have evaluated the efficiency of fine-spaced angled racks associated to a surface bypass entrance to protect fish. Here, 115 salmon smolts and 65 silver eels were radio-tracked over a 2 yr period to assess passage efficiency and passage time at a hydropower intake (50 m3.s−1) retrofitted with a 20 mm rack associated to a surface bypass (2 m3.s−1). Results showed high impediment (89.6% and 96.9% for smolts and eels, respectively), and passage efficiency for the angled rack (89.1% and 93.3%), with short passage times (median, 3 and 7.5 min). However, our results highlighted a strong influence of hydrological conditions, in enhancing fish passage, especially through the bear-trap gate. We conclude that this fish passage solution, making use of existing spillways on the study site, is highly effective for both species. Special attention must, however, be paid to bar-rack design and its cleaning system to ensure fish guidance and prevent impingement or passage through the rack, especially for salmon smolts.

Рыбоходно-нерестовый канал кочетовского гидроузла на реке Дон

The purpose of the research is to develop a layout and design solution for a fish-spawning channel, arranged to bypass the Kochetovsky waterworks on the Don River. Materials and methods. The factual basis of the development was made up of materials of topographic and hydrological surveys, complex surveys of structures and hydrometric studies of discharge regimes of expenses by culverts, data on the functioning of the fish-passing gateway and information on the migratory behavior of fish in the lower reaches of the waterworks. Results and discussion. Based on the initial information on the waterworks, survey and research materials, two alternative variants of the layout and design solution of the fish-spawning channel with its location on the right bank, adjacent to the waterworks, section of the Don floodplain are proposed. According to the first option, the channel is traced mainly along the riverbed (channels) Barsovka, its dimensions are designed to pass a flow rate of – 90 m3/s, with an average flow rate of the water threshold along its path – 0,95 m/s. According to the second variant, the channel is located within the water-protected zone of the Don River along its right bank, the channel path is designed to pass a flow rate of 50 m3/s and is equipped with an additional power supply unit at the inlet head, designed for a flow rate of 40 m3/s. The facilities are equipped with entrance and exit heads, recreation areas for fish and fishing regulators. Both variants of the channel arrangement ensure their functioning according to their purpose – to provide conditions for the passage and spawning of fish. Information is provided on the advantages and disadvantages of each of the technical solutions, the comparison of which allows you to choose one of the options for subsequent development and implementation. Conclusion. 1 Two alternative variants of the layout and design solutions of the Kochetovsky fish-spawning channel have been developed. 2 For further development, it is recommended to trace the channel along the right bank of the Don River with the inclusion of an additional power supply unit ini ts composition.

РЫБОХОДНО-НЕРЕСТОВЫЙ КАНАЛ В СОСТАВЕ КОЧЕТОВСКОГО ГИДРОУЗЛА НА Р. ДОН

Purpose: development of a layout and design solution for a fish passage and spawning channel, arranged as a part of the Kochetovsky waterworks on the river Don. Materials and methods. The factual basis of the development was made up of known information and materials of complex authors’ surveys and studies carried out at the Kochetovsky waterworks according to generally accepted methods. Results. When developing a technical solution for a fish passage and spawning canal, scientific and technical information on the layout and design of the hydraulic structures of the existing Kochetovsky waterworks, data on the hydrology and hydrometry of the investigated section of the river, topographic and other materials were collected, processed and analyzed. It is proposed to contour the canal bypassing the waterworks structures within the right-bank water protection zone of the river with the inclusion of: an inlet head equipped with a mating flume and an additional power supply unit; canal track of a curved shape in a plan, equipped with recreation areas for fish; outlet head with a head regulator that performs the function of the main power unit. A channel arrangement with the following characteristics is proposed: the total flow rate at the fish entry to the channel is 90 cubic m/s; channel track flow rate, provided by the head regulator, 50 cubic m/s and the consumption of an additional power supply unit of 40 cubic m/s; the average water flow velocity in the non-flooded zone of the channel tract is 0.95 m/s; channel inlet flow rate 0.60–1.05 m/s; water depth in the unflooded zone of the canal tract 2.5 m; channel width (trapezoidal section) along the bottom 15.0 m; slopes gradient 2.5; channel length 5850 m. Conclusion. A layout and design solution for a fish passage and spawning canal, arranged bypassing the Kochetovsky waterworks facilities (river Don), organically adapted to the conditions of its creation and providing conditions for passing and spawning of anadromous fish species, has been developed.

Identification of upper thermal thresholds during development in the endangered Nechako white sturgeon with management implications for a regulated river.

Climate change-induced warming effects are already evident in river ecosystems, and projected increases in temperature will continue to amplify stress on fish communities. In addition, many rivers globally are impacted by dams, which have many negative effects on fishes by altering flow, blocking fish passage, and changing sediment composition. However, in some systems, dams present an opportunity to manage river temperature through regulated releases of cooler water. For example, there is a government mandate for Kenney dam operators in the Nechako river, British Columbia, Canada, to maintain river temperature <20°C in July and August to protect migrating sockeye salmon (Oncorhynchus nerka). However, there is another endangered fish species inhabiting the same river, Nechako white sturgeon (Acipenser transmontanus), and it is unclear if these current temperature regulations, or timing of the regulations, are suitable for spawning and developing sturgeon. In this study, we aimed to identify upper thermal thresholds in white sturgeon embryos and larvae to investigate if exposure to current river temperatures are playing a role in recruitment failure. We incubated embryos and yolk-sac larvae in three environmentally relevant temperatures (14, 18 and 21°C) throughout development to identify thermal thresholds across different levels of biological organization. Our results demonstrate upper thermal thresholds at 21°C across physiological measurements in embryo and yolk-sac larvae white sturgeon. Before hatch, both embryo survival and metabolic rate were reduced at 21°C. After hatch, sublethal consequences continued at 21°C because larval sturgeon had decreased thermal plasticity and a dampened transcriptional response during development. In recent years, the Nechako river has reached 21°C by the end of June, and at this temperature, a decrease in sturgeon performance is evident in most of the traits measured. As such, the thermal thresholds identified here suggest current temperature regulations may not be suitable for developing white sturgeon and future recruitment.

Cold-water pollution impacts on two ‘warm-water’ riverine fish: interactions of dam size and life-history requirements

Context Temperature regulates most ecological processes in freshwater ecosystems. Anthropogenic changes to natural thermal regimes, especially cold water released from stratified impoundments (cold-water pollution, CWP), is a widespread and major threat to fish populations globally. Aims Because mitigation options for CWP are often expensive, we aimed to provide robust ecological evidence to inform expenditure. Methods We modelled population responses to CWP remediation for two warm-water fish species (Murray cod and golden perch) downstream of two impoundments (Copeton and Pindari dams) in the semi-arid northern Murray–Darling Basin, Australia. Key results Predicted populations of both species were severely affected by CWP at both sites; however, impacts were species- and site-specific. Effects were greater on golden perch than Murray cod because of their higher temperature requirements for spawning. Predicted spawning opportunities decreased by 77–100% for golden perch and by 38–92% for Murray cod. The larger Copeton Dam had greater impacts than did the smaller Pindari Dam. Conclusions Remediation of CWP can help restore populations and meeting the needs of golden perch may benefit a range of other species. Implications Globally, CWP is a serious threat to warm-water fishes that may compromise and even nullify other restoration efforts. However, restoration may be impeded by current low abundances, angler harvest and restrictions to fish passage.

СУ ШАРУАШЫЛЫҒЫНДА ПАЙДАЛАНЫЛАТЫН БАЛЫҚ ӨТКІЗУ ҚҰРЫЛЫМДАРЫНЫҢ ЖАҢА КОНСТРУКЦИЯЛАРЫ

The paper deals with the research of new structures of concrete hydraulic structures.An important stage in their design is the correct choice of groups of fish passage structures. It is worth noting that the selection of the structure group is carried out mainly on the basis of technical and economic comparisons, and not for structural reasons, taking into account the possibility of fish passing along the entire length of the tract. In the Republic of Kazakhstan, much attention has recently been paid to the development of fisheries. One of the evidences of this is the work of scientists and doctoral students of universities in this field. To create conditions for fish farming in the country, it is necessary to create fish-passing and fish-protection facilities. In any case, we need a new system for the development of fisheries. Indeed, there is no wealth in the fishing industry today. In particular, there is water, little fish. There is a problem here. If there are several reservoirs in the region suitable for fish farming, we will not be able to meet the demand of the residents of the region. If we consider this industry, which forms the basis of the region's economy, as an additional source of income or a subsidiary farm, then it is obvious that the problem will not be solved today or tomorrow.

Hydrodynamic Characteristics of Diagonal Brush Fish Pass: Prototype Measurements

The present study investigates the hydrodynamic characteristics of the diagonal brush upstream fishway at the Incirli run-of-river hydropower plant on Iyidere River in Turkey. Three-dimensional velocity measurements were conducted in the fish pass using a Micro acoustic Doppler velocimeter under real-time operation conditions. The diagonal arrangement of brush blocks creates favorable hydrodynamic conditions (i.e., lateral momentum exchange) that allow fish to minimize swimming energy. We found that the spatially averaged lateral component of Reynolds shear stress is 2.2 times higher than spatially averaged vertical component of Reynolds shear stress, which could be due to the lateral velocity gradient in the vicinity of brush blocks. It is shown that the low-velocity zones behind the brush blocks constitute important resting sites for fish. The monitoring data showed that inlet water levels have considerable effects on the turbulence quantities. The brushes become submerged with the increased reservoir water level from 102 m to 102.05 m above sea level. The maximum turbulent kinetic energy was increased by a factor of three compared to unsubmerged conditions. We found a strong relationship between the average energy dissipation rate per unit mass and the Reynolds number. On the other hand, the prototype data reveal the inverse relationship between the Darcy-Weissbach friction factor and the relative submergence of bristles. The present results allow the efficient design of diagonal fish passes.

Water temperature and precipitation stimulate small-sized Japanese eels to climb a low-height vertical weir.

Although river-crossing structures can have a detrimental effect on the movement and distribution of anguillid eels (genus Anguilla), they have inhabited locations upstream of river-crossing structures in many rivers. However, the growth stage in which the eels start to climb river-crossing structures remains unclear. In this study, we directly observed, using infrared video camera systems, that the Japanese eel (Anguilla japonica) climbs a low-height vertical weir as a migratory barrier, confirming the ability of eels to climb over a low-height weir within a river. All eels climbed the weir at night, between sunset and sunrise. We observed that the total length of Japanese eels that climbed the weir ranged from 60 to 140 mm, suggesting that eels inhabiting the upstream area of a weir climbed it when they were small and then lived and grew upstream. Moreover, the general additive model showed considerable effects of water temperature and precipitation on eel climbing, suggesting that water temperature and precipitation are important for its activation. The results of this study also show the effectiveness of infrared video cameras in monitoring eel climbing, which could be applied to monitor fish migratory behavior through fish passages. The findings of this study are useful for the comprehensive management and conservation of wild eel stocks.

Application of Tesla Valve’s Obstruction Characteristics to Reverse Fluid in Fish Migration

More and more activities have caused significant damage to the river environment, among which a typical problem of blocked fish migration is constantly attracting people’s attention. Nowadays, fishways are essential hydraulic facilities to solve such problems. Although a different fishway has a particular blocking effect on the water flow, the flow velocity of the vital positions of fish migration in the fishway could still be relatively high locally, which may pose a certain challenge to the fish migration (the higher flow velocity could lead to the increase in migratory energy consumption of fish). Therefore, further exploration of fish passing facilities may be required. As a check valve without movable parts, the Tesla valve is expected to be used in fish passing facilities because of its substantial obstruction to the reverse flow of internal fluid. This paper conducted numerical simulation experiments on the fish passage pipeline designed based on Tesla valves using the RNG (renormalization group) k-ε model. Grass carp were selected as the primary analysis object, and the simulation results were analyzed from the perspective of turbulence characteristics. The results showed that the fish passage pipeline based on the T45-R Tesla valve was better than that on the GMF (Gamboa, Morris and Forster) Tesla valve in velocity control. The velocity at the vital position of T45-R internal fluid was about 20% lower than that of GMF. The results of the velocity cloud diagram showed apparent high-velocity and low-velocity areas in the fish passage pipeline designed based on the T45-R Tesla valve. The high-velocity area was the vital position for fish upstream, and the maximum velocity variation range in this area was 0.904~1.478 m/s. At the same time, the flow in the low-velocity area is almost static water. The analysis illustrated that the resulting velocity environment could provide conditions for grass carp to move upstream successfully. The results of turbulent kinetic energy inside the fish passage pipeline showed that the maximum value of turbulent kinetic energy was only about 0.043 m2/s2, which could be friendly for fish upstream. In addition, the results show that pressure-related problems could not seem to have an excessive impact on fish migration, such as causing damage. Overall, the results further studied the feasibility of using the Tesla valve as a fish passage pipeline.

Three-dimensional migratory behaviour of European silver eels (Anguilla anguilla) approaching a hydropower plant.

The global population of European eel (Anguilla anguilla) is rapidly declining, and migration barriers in rivers are believed to be one of several key causes. While progress has been made in the development of bypass solutions, they are often constructed based on a limited knowledge of swimming behaviour. A bypass close to the stream bed is often recommended at fish passage facilities to accommodate downstream eel migration. The results of this recommendation are poorly studied, and the few studies that exist show varying bypass efficiencies. The current study used acoustic telemetry with depth sensors to explore the three-dimensional migratory behaviour of downstream-migrating silver eels. The eels were tracked as they approached a hydropower plant with a state-of-the-art angled bar rack and full-depth bypass. Downstream and upstream swimming differed in preferred vertical and lateral positions. During periods of local downstream movement, the density of observations was largest in the upper middle section, away from the river boundaries and in higher velocities. Conversely, when moving upstream, eels tended to avoid the upper layers of the middle part of the river, swimming closer to the riverbed and using the bank areas to a greater extent. Downstream-moving fish swam higher in the water column during night and in turbid conditions (high discharge). When approaching the impassable bar rack and the full-depth bypass, the eels searched most intensely but not exclusively along the bottom third of the rack, often exploring at new depths after changing direction. The impediment passage efficiency was 100% when both bypass solutions were considered. The study provides knowledge of the swimming behaviour of silver eels, which is relevant for the design of bypass solutions for eels at migration barriers.

Impact of hydraulic forces on the passage of round goby (Neogobius melanostomus), gudgeon (Gobio gobio) and bullhead (Cottus gobio) in a vertical slot fish pass

AbstractEvery fish migrating upstream through vertical slot fish passes must swim through slots, where the resistance force of flowing water could affect the passage success. We measured the hydraulic force acting on the body of preserved benthic fish in a vertical slot at different water discharge rates (80 and 130 L/s) to compare the hydraulic burden individual fish species (round goby Neogobius melanostomus Pallas, 1814, gudgeon Gobio gobio L. and bullhead Cottus gobio L.) must overcome. The forces measured in three spatial axes were then compared to acoustic Doppler velocity measurements and the passage probability of 39–45 live fish per species. Passage probability reduction of 28.26% for round goby and 39.29% for bullhead was observed at the higher water discharge. Gudgeon showed increased numbers of passages and approaches when larger hydraulic forces were experienced at 130 L/s compared to the lower water discharge. Gudgeon experienced significantly lower hydraulic forces (mean 0.27 N ± 0.12 standard deviation) compared to round goby (mean 0.32 N ± 0.12 SD) and bullhead (0.35 N ± 0.14 SD). Potentially, the increased hydraulic forces at the higher water discharge contributed to the reduction in passages in round goby and bullhead. That gudgeon behaved differently from the other species illustrates how fish species deal differently with flowing water and the hydraulic forces experienced. Our approach provides a species‐oriented assessment of the flow field in ecologically relevant fish passes. These findings represent an important step towards the development of purposeful fish pass designs, which is essential for ecosystem‐oriented river connectivity.

Аbout the influence of the use of «zaezdok» type nets on the passing of the Рacific salmon producers to the springing territories in the Аmur and Аmur liman

Materials are presented on the study of the technology of harvesting Pacific salmon, using fixed seines of the «zaezdok» type in the Amur estuary and the river. Amur, in order to ensure the passage of spawners of Pacific salmon during passing days without dismantling the wings and the trap, but only by closing the inlet device of the reservoir. The results of the conducted studies showed that the design of a fixed seine of the «zaezdok» type does not prevent the passage of fish to spawning grounds, does not allow it to be bound and does not cause damage to the prey object. During periods of skipping spawners («passing days»), it is sufficient to close the entrance to the seine trap and raise its netting. This ensures the unhindered exit of fish from the fishing area of the prey tool. Installation of additional structural elements (windows, etc.) is not required to ensure the passage of fish.

Redesign of an Intake Fish Pass Structure

Abstract The article describes the process of redesigning the intake structure of the fish pass at the Žilina water structure in Slovakia. The existing intake structure does not meet the passability requirements for the target species of migratory fish. A design utilizing intake windows at various levels that cover fluctuations in the water level in the reservoir, which has been successfully used for other water structures, has been proposed. The new design was subjected to hydraulic calculations and simulations in the HECRAS 2D, 2D numerical model in order to achieve the required parameters such as the discharges, depths, and velocities within the limits for the specified fish zone.