Improve Fish Passage Research Articles

Not all who meander are lost: migrating sea lamprey follow river thalwegs to facilitate safe and efficient passage upstream.

Efficient navigation is crucial for the reproductive success of many migratory species, often driven by competing pressures to conserve energy and reduce predation risk. Little is known about how non-homing species achieve this balance. We show that sea lamprey (Petromyzon marinus), an ancient extant vertebrate, uses persistent patterns in hydro-geomorphology to quickly and efficiently navigate through complex ecosystems. Hydrodynamic flow models coupled with bathymetric mapping and fine scale acoustic telemetry revealed movement paths that tracked thalweg scour channels promoting rapid and efficient upstream migration, suggesting the existence of a bathymetric highway system. Near-substrate swimming along this path resulted in a median of 5.8% energy savings while also promoting improved safety from nocturnally active predators. We hypothesize sea lampreys use a novel mechanism, hydrostatic pressure guided rheotaxis, to achieve this navigation. It is likely this tactic relies on sensory information from the animal's primitive lateral line and perhaps the inner ear. Insights from this study can be used to redesign conservation practices to achieve improved control where the animal is invasive and improved fish passage within its native range.

Indications of recovery of anadromous fishes in a mid‐Atlantic estuary of North America: Spatial and seasonal patterns near a dam

AbstractObjectiveRivers on the east coast of North America once supported vast runs of anadromous fishes, such as Blueback Herring Alosa aestivalis and American Shad A. sapidissima. Declines in runs were attributed to, in part, dams and poor water quality that have since been improved by fishways and improvements to wastewater treatment, respectively. The goal of this study was to determine the status of anadromous fishes upstream and downstream of a dam in a heavily urbanized tributary that has undergone improvements in fish passage and water quality.MethodsWe used boat electrofishing to index fish densities during the spring and summer over 2 years.ResultWe found a substantial run of anadromous Blueback Herring, a species that was extirpated in the 1970s but observed in low numbers in the 1990s and early 2000s. We also found a general pattern of decreasing densities of Blueback Herring and Striped Bass Morone saxatilis upstream of the dam than downstream, suggesting that the dam remains a major impediment to the full recovery of Blueback Herring and other anadromous fishes despite a fish ladder being installed in 1998.ConclusionOur study demonstrates that highly urbanized rivers, such as the Cooper River, can and in some cases do support substantial runs of anadromous fishes. It is important that urban waters be considered for restoration efforts such as improved fish passage to increase access to historical spawning grounds if these fisheries are to recover. Continued monitoring of urbanized streams and tidewater is needed to better describe the long‐term responses of anadromous fishes to efforts that ameliorate threats caused by urbanization.

Swimming behaviour of Atlantic salmon kelts migrating past a hydropower plant dam: Effects of hydraulics and dam operations

Hydropower plants commonly impede the downstream migration of Atlantic salmon (Salmo salar) kelts. Thus, understanding the effects of hydraulic conditions on kelt behaviour and passage performance at dams is crucial for developing effective mitigation measures. In this study, we investigated the influence of hydraulic conditions on kelt passage performance and swimming behaviour at a Norwegian hydropower plant. We combined biological data from 48 kelts collected via acoustic telemetry with hydraulic data modelled using computational fluid dynamics. We assessed kelt passage performance using metrics such as time-to-pass, total number of detections, and total number of detections per day. Additionally, we analysed swimming depths and speeds in relation to the hydraulic conditions created by different dam operating conditions. We found that the dam operation schedule impacted the kelts' ability to find a route past the dam. Though kelts could have passed the dam throughout the study period via a submerged pipe at the dam (which had seemingly sufficient discharge for the kelts to find), 98% of the kelts instead waited for a spill gate to open partway through the study period. The swimming depth analysis indicated diel variation, with kelts swimming nearer to the water surface during the night. We found that swimming speed increased with increasing kelt body length, particularly under high turbulence kinetic energy and during the day. Furthermore, kelts swam faster as water velocity increased, but slowed down again as turbulence intensity increased. Our findings reveal the effects of hydraulic conditions and dam operations on the migration behaviour of Atlantic salmon kelts. This provides valuable insights for developing strategies to optimise dam operations and improve fish passage performance, including the need to spill enough water to increase passage success and will contribute to sustainable management of Atlantic salmon populations in regulated rivers.

Short-term growth, movement and response of European eel Anguilla anguilla to re-meandering of a small English chalk stream

In recent decades, the population of European eel Anguilla anguilla has strongly declined and the stock is outside safe biological limits. Freshwater habitat degradation has been cited as a key causal factor in the European eel decline, but there are limited studies assessing the responses of this species to river habitat restoration efforts. This study utilized mark-and-recapture data from annual electrofishing surveys conducted between 2009 and 2014 to describe European eel population density and size structure (length, weight) in the River Glaven − a chalk stream in eastern England. Short-term effects of river restoration on European eel were assessed via a Before-After-Control-Impact experimental design. Of the recaptured individuals, 73% were sedentary and the rest mobile. Despite re-meandering work increasing habitat heterogeneity in the restoration reach relative to the control reach, no change in European eel density or size structure was detected across treatments and time. While length and weight increased in the downstream control reach over the study period, density declined. This can be attributed to various local stressors such as barriers to European eel migration, as well as broader range-scale causes including climatic and oceanic factors. Although further research is ideally necessary to ensure adequate sample sizes, as well as to provide long-term monitoring of eel responses to river restoration, this study emphasizes the need for whole-catchment efforts in European eel conservation that combine river–floodplain restoration with greatly improved fish passage.

Benefits from recreational catch improvements may hinge on fish consumption safety: Evidence from the Cape Fear River, North Carolina

Benefits from recreational catch improvements may hinge on fish consumption safety: Evidence from the Cape Fear River, North Carolina

Machine learning based assessment of small-bodied fish tracking to evaluate spoiler baffle fish passage design

Fish passage research is important to mitigate the adverse effects of fragmented river habitats caused by waterway structures. The scale at which this research is undertaken varies from small-scale laboratory prototype studies to in-situ observations at various fish passage structures and bottlenecks. Using DeepLabCut, we introduce and evaluate a machine learning based workflow to track small-bodied fish in order to facilitate improved fish passage management. We specifically studied the behaviour and kinematics of Galaxias maculatus, a widespread diadromous Southern Hemisphere fish species. Upstream fish passage was studied in the presence of three different patches of spoiler baffles at an average water velocity of 0.4m/s. In semi-supervised mode, the fish locations were extracted, and fish behaviour, such as swimming pathways and resting locations, was analysed based on extracted positions and recorded kinematic parameters. Individual fish behaviour and kinematic parameters were then used to assess the suitability of the three different spoiler baffle designs for enhancing fish passage. Using this technique, we were able to demonstrate where different spoiler baffle configurations resulted in significant differences in fish passage success and behaviour. For example, medium-spaced smaller baffles provided more accessible and uniform resting locations, which were required for efficient upstream passage. Results are discussed in relation to fish passage management at small instream structures.

Group size influences light‐emitting diode light colour and substrate preference of David's Schizothoracin (Schizothorax davidi): Relevance for design of fish passage facilities

AbstractFish passage structures have been constructed to facilitate fish movement past barriers, though the effectiveness of passage structures is highly variable. Designing fish passage structures that consider the behavioural preferences of fish under different environmental conditions (e.g., light colour, substrate type) has the potential to improve fish passage success. Similarly, whether a fish encounters a passage facility alone or in a group may influence fish behaviour. In this case, we assessed the preference of different group sizes (n = 1, 6 and 12, respectively) of David's Schizothoracin Schizothorax davidi under four different light‐emitting diode colours and eight different substrate types in the aquaria of the Houziyan Reproduction Station. We found that singletons preferred to visit the white light, cement and fine pebble, while the fish in groups preferred to visit the blue light, fine pebble and cobble. In addition, the total percentage of mobility frequency (18.3 ± 1.8%), movement velocity (20.4 ± 15.9 cm/s) and distance moved (15.8 ± 1.8 m) of singletons in blue light were much lower than that in the others. The movement velocity (3.3 ± 0.6 cm/s) of singletons on cobble was less, but the percentage of total mobility time (162.9 ± 16.0%) and distance moved (153.4 ± 19.6 m) on the cobble were much greater. Our research yielded novel insights for improving passage efficiency for this species. Findings from this study suggest there should be greater consideration of light colour and substrate type when designing fish passage facilities. Because fish almost always experience dynamic hydraulic conditions near and in fishways, additional research is needed to understand the generality of these findings in systems under lotic characteristics.

Influence of operation modes and fish behavior on fish passage through turbines

The assessment of fish passage through turbines is important to develop cost-efficient environmental solutions and strategies that avoid individual fish injuries and, therefore, enhance the fish population development in a catchment. As part of the FIThydro project, fish passage analysis were performed for the bulb turbine in Bannwil, the S-turbine in Guma and the bulb unit at the test facility in Obernach.Numerical modelling in principle provides the most comprehensive information on hydrodynamic conditions in the turbine passage. Many details of the main relevant stressors on fishes can be derived. The information of different stressors like pressure, strike, shear and turbulence can be extracted with high accuracy assuming that a fish pathway follows a streamline through the turbine. The accurate prediction of the stressors and the validation with measurements enables the designer to develop a turbine that reduces the stress on the fish and, hence, increase the fish survival rate.The survival rate also strongly depends on biological aspects of a fish species. Besides the reaction of the fish on the different stressors, complex parameters like swim behavior or preferred swim elevations are of high importance on the survival rate. However, these parameters vary among different fish species.CFD simulations of different turbines are performed and simulation results were compared to measurements with the Barotrauma Detection System (BDS) sensors at the test cases in Guma and Bannwil, as well as live fish tests at the test facility in Obernach. The fish behavior was modeled in the CFD based evaluation method. Studies related to swimming speed, fish orientation and especially the actual passage location demonstrate the sensitivity of these parameters on the fish survival rate. Another aspect was the influence of operating conditions on fish passage. A wide spectrum of operating conditions was analyzed and fish passage hill-charts for different stressors were generated. This knowledge enables an adapted power plant operation related to migration movements of certain fish species. The CFD based analysis method shows to be a powerful tool to improve fish passage through a turbine by changing hydraulic design and by adapting operational modes. Relative improvements to conventional designs and operation can be quantified.

Multislot Fishway Improves Entrance Performance and Fish Transit Time over Vertical Slots

Pool-type fishways have been increasingly tested to improve fish passage performance and minimize migration delays. Designing cost-effective fishways is essential for a trade-off between water uses and successful longitudinal connectivity restoration. The multislot fishway (MSF) concept, which operates with 30–50% lower discharge than a vertical slot fishway (VSF), was recently developed. This study assessed and compared the entrance performance (entrance time; entry efficiency) and transit times of two cyprinids for VSFs and MSFs. Four configurations, with the same structural characteristics (slope; water depth; head drop; pool width and depth), operating with different discharges (Q), were tested (VSF 1: Q = 112 L·s−1; VSF 2: Q = 80 L·s−1; MSF 1: Q = 58 L·s−1; MSF 2: Q = 37 L·s−1). Hydrodynamics characterization was performed using a numerical model. Results showed that entry efficiency was higher in MSFs than in VSFs, while entrance time and transit time were overall lower. Numerical modelling revealed that velocities were around 30% lower in MSFs, and turbulence could reach a difference of around 70% in Reynolds shear stress and 50% in turbulent kinetic energy. Overall, MSFs can be considered as a cost-effective fishway solution that can balance the trade-offs between divergent interests in water uses.

Improving bypass performance and passage success of Atlantic salmon smolts at an old fish-hostile hydroelectric power station: a challenging task

Old hydroelectric power stations often provide unsafe migration routes to fish, apart from passing through mobile gates during high flow. The installation of retrofitted bypass is considered to be a potential solution to improve fish passage at such old structures, but their performances are often insufficient. In the Amblève River (Belgium), a mobile 3.3 m high dam feeds two principal Francis turbines (12 + 14 m3 s−1) and is equipped with three mobile gates, a modern vertical slot upstream fish pass and a retrofitted downstream bypass functioning at a very low flow (1% of maximum turbined flow). A bypassed river section (length 8.4 km) downstream of the dam was set at 3 m3 s−1 and supplies a Francis microturbine. From 2015 to 2016, we used 1150 hatchery Atlantic salmon smolts (Salmo salar), and we placed antennae with automatic radio-frequency identification (RFID) stations to analyse the migration routes used (n = 5). We tested the attraction efficiency and the performance of the bypass with and without the placement of a guidance system at the entrance and examined the proportion of smolt passage at the different migration routes under three functioning configurations. The placement of the guidance system markedly improved the attraction efficiency and the overall passage efficiency. The median time spent at the entrance of the bypass was from 7 to 12 min, and the time spent near the entrance of the bypass was less than 1 h for 67.1% (release 1), 88.2% (release 2) and 63.7% (release 3) of the smolts. During the three release events, the smolts arrived near the entrance of the bypass mostly during the dusk and dark periods (87.5%, 96.0% and 95.5%, for releases 1, 2 and 3, respectively). In a configuration without opening a mobile gate, the bypass was the most used migration route, followed by the microturbine and the main turbine. Stopping the microturbine and opening a mobile gate has consequences of making it the first choice of passage followed by the main turbine and the bypass. The re-establishment of safe and quick downstream migration has to be considered with a holistic view of the functioning of the hydroelectric powerstation.

Mechanical harvester removes invasive aquatic weeds to restore water quality and fish habitat values on the Burdekin floodplain

Removal of approximately 5 ha of an aquatic weed in late 2016 rapidly improved water quality in a 7 km section of creek on the Burdekin floodplain, northern Queensland – one of many creeks feeding into the Bowling Green Bay RAMSAR wetland. Numbers of native fish species found in the creek increased from one species prior to treatment to 15 species within 2 years. This project concluded that removal of weed blocks to re‐oxygenate water and improve fish passage is one important action towards improving environmental conditions of floodplains in the Great Barrier Reef catchments, as long as there is ongoing weed follow up.

Interactions between water depth, velocity and body size on fish swimming performance: Implications for culvert hydrodynamics

Understanding how fish traverse man-made barriers (e.g. road-crossings and culverts) ensures that engineering and design guidelines achieve positive outcomes for fish communities. Water velocity, depth and fish body size are interrelated factors that influence fish passage through culverts. Velocity barriers have been a major focus of culvert remediation efforts to improve fish passage, however wide culvert designs that aim to limit high water velocities, often create shallow depths in the culvert barrel that can potentially impede fish passage. Here, we quantified how water velocity, depth and body size interact to affect fish swimming performance and their ability to traverse a 12 m culvert-scale swimming channel. Juveniles and sub-adults of three large-bodied native Australian fish species, silver perch (Bidyanus bidyanus), Murray cod (Maccullochella peelii) and eel-tail catfish (Tandanus tandanus), were chosen to represent a range of body shapes, swimming styles and capabilities. Each species was swum in nine treatments, consisting of three velocities at three water depths, with their time to fatigue and traverse success rates over 8 m of flume length quantified. We found that B. bidyanus had an exceptional probability of traverse success, with larger individuals traversing faster than smaller sized fish, but they were physically hindered by shallow water depths. The interaction between velocity and depth was non-linear and highly affected the swimming performance and traverse success of M. peelii and T. tandanus, particularly for fish >250 mm and < 100 mm. Our results demonstrate the importance of considering size class and species-specific swimming capabilities in culvert design criteria.

Using knowledge of behaviour and optic physiology to improve fish passage through culverts

AbstractCulverts reduce connectivity for aquatic animals by being both a hydraulic and physical barrier. However, altered light intensity may also be a behavioural barrier to fish movement, especially for diurnal species that have adapted to moving when it is light. We propose that knowledge of optical physiology and fish behaviour, two important mechanisms underpinning movement, can inform efforts to improve fish movement through culverts. We firstly review the sensory systems of fish with reference to visual sense and explore how this affects fish movement. We then highlight theoretical knowledge that can help us understand fish behaviour and the potential mismatch between the conditions under which fish have evolved and altered conditions within culverts. We describe potential knowledge gaps and directions for future research to improve our understanding of how culverts may affect fish movement. Finally, we explore the potential costs and ecological benefits of different mitigation options to identify those with the most promise for managing the light environment in culverts to facilitate movement. For researchers and managers exploring this subject, we suggest an approach that: (a) identifies light requirements for movement by different species, (b) tests movement under different light conditions and (c) considers an integrative assessment method for testing fish behaviour around culverts. Understanding how optical physiology, fish behaviour and culvert design influence fish movement can improve connectivity for a range of species.

Changes in Fish Assemblages at the Mirror Lake Complex in the Lower Columbia River Before and After a Culvert Modification

Abstract Changes in fish assemblages were examined before and after a culvert was modified to improve the fish passage at the Mirror Lake Complex (MLC), located along the Columbia River Gorge, Oregon. Conditions at the culvert limited water flow between the Columbia River and the MLC during certain portions of the year; thus, the outlet and interior of the culvert were modified to improve fish passage. Prior to the culvert modification, three sites were sampled monthly between April and August 2008, 5.0 km and 0.5 km upstream of the culvert and immediately downstream of the culvert. Following the culvert modification in the late summer of 2008, the same sites were sampled from 2009 to 2012, with two additional sites added in 2010. Prior to the culvert modification, the lower sites (i.e., the sites closest to the Columbia River) supported native and nonnative fish species, while the upper sites were dominated by native species. During the 4 years of monitoring after culvert modification, these distinctions between the upper and lower sites remained. A significant increase in water temperature and species richness was observed at the site just upstream of the culvert, but other changes in fish composition (density, diversity, percent of nonnative species) were not observed. However, at the upper sites, while nonnative species were absent before culvert modification, they were present after modification. Modifications made at the culvert, in combination with seasonal variation in water level and water temperature, may have influenced fish communities in the MLC. Given predicted regional and global climatic changes, our study indicates the importance of long-term monitoring of restoration sites for the presence of nonnative species and the effects of environmental variables, such as water temperature.

Swimming Performance of Rainbow Trout and Westslope Cutthroat Trout in an Open-Channel Flume

AbstractWe used an open-channel flume to characterize the swimming performance of Rainbow Trout Oncorhynchus mykiss and Westslope Cutthroat Trout Oncorhynchus clarki lewisi ranging nominally in fork length from 15 to 30 cm. With an open-channel flume, we observed volitional swim performance of wild-caught Rainbow Trout and Westslope Cutthroat Trout; the fish were not coerced, prodded, or spooked into action. We also observed the maximum short-duration swim speed of the fish, providing important effective leap or velocity challenge information for the design of intentional barriers. We conducted the experiment with a consistently low water velocity challenge and characterized swim speeds by using weighted least-squares regression, revealing no evidence of a difference in swim speeds between the two species. We estimated the overall average swim speed for Rainbow Trout to be 0.84 m/s (SE = 0.02), with a 95% confidence interval of 0.79–0.89 m/s, and that for Westslope Cutthroat Trout to be 0.84 m/s (SE = 0.03), with a 95% confidence interval of 0.78–0.90 m/s. The maximum swim speeds observed were 2.72 m/s for Rainbow Trout and 3.55 m/s for Westslope Cutthroat Trout. The project results provide new information on the swimming ability of wild Rainbow Trout and Westslope Cutthroat Trout that can be used to improve fish passage or barrier design.

A dam passage performance standard model for American shad

Objectives for recovery of alosines commonly involve improving fish passage at dams during migration. However, a quantitative basis for dam passage performance standards is largely absent. We describe development of a stochastic life-history-based simulation model for American shad, Alosa sapidissima, to estimate effects of dam passage and migratory delay on abundance, spatial distribution of spawning adults, and demographic structuring in space and time. We used the Penobscot River, Maine, USA, as a case study to examine sensitivity of modeled population metrics and probability of achieving specific management goals to inputs. Spawner abundance and percentage of repeat spawners were most sensitive to survival and migration delay at dams, marine survival, and temperature cues for migratory events. Recovery objectives related to abundance and spatial distribution of spawners were achievable under multiple scenarios, but high rates of upstream and downstream passage were necessary. The simulation indicated trade-offs between upstream and downstream passage efficacy whereby increased downstream passage was required to maintain or increase population abundance in conjunction with increased upstream passage. This model provides a quantitative support tool for managers to inform ecologically based decisions about a suite of management scenarios to facilitate recovery and sustainability of diadromous fish populations.

Fish passage developments for small-bodied tropical fish: field case-studies lead to technology improvements

In tropical coastal lowland rivers, there are frequently biodiverse upstream migrations of post-larval and juvenile diadromous fish from estuaries into freshwater. Tidal barriers completely block major migratory pathways for these fish and have contributed to major losses of freshwater biodiversity. In northern Australia, early efforts to improve tropical river fish passage with salmonid-style fishways completely failed. Since the mid-1990s, low gradient vertical-slot and rock fishways improved fish passage but the smallest and most abundant fish (i.e. from 10 to 100 mm long) often still failed to ascend. Since the mid-2000s, there was a paradigm shift in hydraulic design criteria for new fishways, with a renewed focus on: (i) low turbulence, (ii) maximized roughness and hydraulic boundary layers to optimise fish ascent. We used a combined methodology, firstly developing a conceptual model of fish movement to inform fishway design criteria, secondly tabulating past and present fishway design criteria, and thirdly conducting a series of brief field case-studies, at tidal barriers in tropical rivers for new technical and rock fishways. Our objective was to evaluate the success of these new designs for passage of very small (from 9 mm long) diadromous fish on low head barriers (i.e. <3 m high). We conclude that while there have been improvements in passage of small-bodied fish at tidal barriers further experimental work is still needed to test and refine current ecohydraulic fishway design criteria.

Fish passage hydrodynamics: insights into overcoming migration challenges for small-bodied fish

The modification and utilization of rivers in regions where small-bodied diadromous fish are prevalent has largely occurred without fully understanding the migration behaviour of these species. As a result, existing in-stream structures often prevent or restrict migration. Current fish passage design guidance generally focuses on providing average hydrodynamic conditions within the range of known critical swimming velocities for target fish species. Considerable portions of discharge capacity must be sacrificed to achieve average cross-sectional water velocities that will allow passage of weak swimmers. Furthermore, because the hydrodynamic requirements for small-bodied species are poorly understood, successful passage is still not guaranteed even when average hydrodynamic design criteria are met. Ethohydraulic research is focused on how water flow influences fish behaviour and vice versa, by studying the interaction of fish with small-scale in-flow characteristics. We discuss how an ethohydraulic approach may improve fish passage design for small-bodied fish, such as țnanga/common galaxias (Galaxias maculatus), a widespread diadromous Southern Hemisphere species. The ethohydraulic approach is discussed in detail for culverts, a commonly found structure known to impede fish passage for many small-bodied species.

Assessing and Prioritizing Barriers to Aquatic Connectivity in the Eastern United States

AbstractThere are tens of thousands of dams and millions of road‐stream crossings in the eastern United States (U.S.) which can prevent fish and other aquatic organisms from accessing key habitats. There is growing momentum in the eastern U.S., and throughout the country, to remove dams which no longer serve their intended purpose, provide improved fish passage facilities at those dams that cannot feasibly be removed, and upgrade road‐stream crossings to benefit aquatic organism passage (AOP). However, these projects are expensive and given the extensive scope of the problem and the limited resources available to address it, it is imperative to be strategic in deciding which barriers are removed or upgraded. The Nature Conservancy, in conjunction with several partners, has conducted a suite of analyses which assess and prioritize barriers to AOP for the potential ecological gains that could be realized if they were removed or upgraded. The results of these analyses have been used both proactively and reactively by managers throughout the eastern U.S. to identify potential connectivity restoration projects, support funding requests, and help inform funding allocation decisions by providing a common evaluation system for the many thousands of potential projects. In contrast to more prescriptive barrier removal optimizations, their flexibility of use provides managers with a practical framework for planning aquatic connectivity restoration while remaining open to the element of opportunity.

Hydraulic and biological characterization of a large Kaplan turbine

Abstract One of the most cost-effective and environmentally sound methods of developing hydropower is through the uprating of hydroelectric turbines. In many countries hydroelectric dams have turbines that are approaching their expected service life, with plans underway to install replacement turbines that are expected to improve fish passage survival. To validate these improvements, there is a need to develop a baseline hydraulic characterization of existing Kaplan turbines. An autonomous sensor device known as the Sensor Fish was deployed at Ice Harbor Dam to characterize the hydraulics under different operating conditions. Nadir pressures varied by operating condition, with values decreasing with operating power (144–106 kPaA). Pressure changes during turbine passage varied by operating condition, with values increasing with operating power (311–344 kPa). There were slightly more significant events (acceleration ≥95G) in the stay vane/wicket gate region than the runner region. Rotational velocity data were similar between operating conditions. Sensor Fish data amassed during field studies in similar turbines were used for comparison. This study offers critical insights into the biological performance of large Kaplan turbines and provides vital information that can be used to make informed decisions that lead to additional design or operational improvements.