Fishway Passage Research Articles

Technical fishway passage structures provide high passage efficiency and effective passage for adult Pacific salmonids at eight large dams

Fishways have been widely used for upstream passage around human-built structures, but ‘success’ has varied dramatically. Evaluation of fishway success has typically been conducted at local scales using metrics such as fish passage efficiency and passage time, but evaluations are increasingly used in broader assessments of whether passage facilities meet population-specific conservation and management objectives. Over 15 years, we monitored passage effectiveness at eight dams on the Columbia and Snake rivers for 26,886 radio-tagged spring-summer and fall Chinook Salmon O. tshwaytscha, Sockeye Salmon O. nerka, and summer steelhead O. mykiss during their migrations to spawning sites. Almost all fish that entered dam tailraces eventually approached and entered fishways. Tailrace-to-forebay passage efficiency estimates at individual dams were consistently high, averaging 0.966 (SD = 0.035) across 245 run×year×dam combinations. These estimates are among the highest recorded for any migratory species, which we attribute to the scale of evaluation, salmonid life history traits (e.g., philopatry), and a sustained adaptive management approach to fishway design, maintenance, and improvement. Full-dam fish passage times were considerably more variable, with run×year×dam medians ranging from 5–65 h. Evaluation at larger scales provided evidence that fishways were biologically effective, e.g., we observed rapid migration rates (medians = 28–40 km/d) through river reaches with multiple dams and estimated fisheries-adjusted upstream migration survival of 67–69%. However, there were substantive uncertainties regarding effectiveness. Uncertainty about natal origins confounded estimation of population-specific survival and interpretation of apparent dam passage ‘failure’, while lack of post-migration reproductive data precluded analyses of delayed or cumulative effects of passing the impounded system on fish fitness. Although the technical fishways are effective for salmonids in the Columbia-Snake River system, other co-migrating species have lower passage rates, highlighting the need for species-specific design and evaluation wherever passage facilities impact fish management and conservation goals.

The role of individual behavioral traits on fishway passage attempt behavior.

Variations in behavioral traits are widely recognized to drive animal behaviors exhibited within a population. However, information on how behavior traits influence behavior in anthropogenically modified habitats is lacking. Many habitats have become highly fragmented as a result of human processes. To mitigate this and improve habitat connectivity, wildlife passes are increasingly employed, with the aim of enabling animals to move freely between habitats. However, wildlife passes (e.g., fishways) are not always effective in achieving passage and it remains uncertain what factors play a role in an individual's likelihood of passing successfully. This study measured three behavioral traits (boldness, exploration, and activity) in juvenile brown trout (Salmo trutta; n = 78) under field conditions within a river and tested whether these behavior traits influenced both the passage success and the behaviors exhibited during upstream fishway passage attempts. Although behavioral traits were found and collapsed into two behavioral trait dimensions, behavioral traits had low repeatability and so did not contribute to a personality spectrum. Boldness was found to negatively influence the number of passage attempts carried out by an individual and to positively influence passage success, with bolder individuals carrying out fewer attempts and having an increased probability of passage success. No behavioral traits were found to be related to other passage metrics (passage success, Time until First Attempt, and Passage Duration) during the first passage. But all three behavioral traits were significantly negatively related to the changes in passage behaviors at consecutive, successful passage attempts, with bolder, more exploratory and more active individuals passing through a fishway quicker on the second passage than on the first. This study suggests that bolder and more active individuals may perform better during fishway passage attempts, particularly within rivers where multiple barriers to movement exist.

Fish passage assessment in stepped fishways: Passage success and transit time as standardized metrics

Fishways are used worldwide to restore fish migration routes. However, there are few standardized metrics that allow the comparison of their performance in a consistence manner. This paper aims to assess fishway internal passage using two standardized metrics: passage success and transit time. Data from selected 20 field stepped fishways evaluation were gathered from a systematic review and own field experiments, considering potamodromous species as target fish. The influence of main biological and hydraulic parameters on these metrics was analyzed and modeled by logistic regression and survival analysis techniques. Passage success and transit time described reliably fishway performance. Both metrics were significantly influenced by fishway type, volumetric power dissipation, height drop between pools, slope, obstacle height, pool depth, species and fork length in fishway passage. This work may serve as a guide for all engineers and managers working in fishway assessment, design and management to assess and compare other fishways, select proper design parameters and open the discussion and future research on these topics.

Rapid Migration and High Survival of Adult Pacific Lampreys in Reservoirs

AbstractDams and reservoirs present diverse hazards for riverine fishes, including slowed migration, reduced or blocked access to essential habitats, and direct and delayed mortality risks. Many of these hazards are evident for Pacific Lamprey Entosphenus tridentatus in the heavily dammed Columbia River basin, where the species’ distribution and abundance has sharply declined. In a 3‐year study, we used acoustic telemetry to investigate behavior and apparent survival of 784 adult Pacific Lampreys in Columbia River reservoirs and turbulent dam tailraces, two environments where previous monitoring efforts have been somewhat ineffectual. We released Pacific Lampreys upstream and downstream from Bonneville Dam to test whether Pacific Lamprey passage at one dam negatively affected upstream dam and reservoir passage metrics (i.e., delayed effects on migration rate or reach passage success) and whether upstream‐released groups migrated further than their downstream‐released counterparts. Overall, results showed that Pacific Lampreys migrated very rapidly (median rates = 50–62 km/d) in reservoir reaches and slowly (1–3 km/d) in reaches with tailraces or fishways. Pacific Lampreys also had much higher passage success in reservoir reaches (reach × year estimates = 0.93–0.99) than in reaches with tailraces or fishways (most estimates = 0.58–0.82). We found little statistical evidence for negative delayed effects of dam passage. Pacific Lampreys released in the Bonneville forebay were far more likely to pass upstream dams (~26–57%) than were those released in the Bonneville tailrace (~20–36%). We conclude that tailraces and fishways constrained the upstream distribution of adult Pacific Lampreys, that reservoirs were not associated with high mortality during active upstream migration, and that translocation past individual dams can increase the upstream migration distance of individuals and population distribution. Areas of continuing uncertainty include behavior and survival during overwintering (i.e., prespawn holding) and the potential delayed effects of tailrace and fishway passage on Pacific Lamprey fitness.

A New Paradigm in Alewife Migration: Oscillations between Spawning Grounds and Estuarine Habitats

AbstractThe current paradigm in Alewife Alosa pseudoharengus migrations is shifting from a single reproductive event and rapid movement in and out of freshwater to one that recognizes more nuanced movements and asynchronous batch spawning. In this study, Alewives (n = 72) were acoustically tagged in the Carmans River, Long Island, New York, a small coastal river with restored fish passage. Our objective was to examine fine‐scale spatial movements in the tidal and reconnected habitats to identify spawning behavior patterns, including habitat use and spawning periodicity, that can be applied to fishway restoration and species management. Alewives that completed their spawning migration (n = 27) exhibited variability in posttagging trajectories, residency, passage rate, and behavior. The current paradigm consisting of a single upstream migration followed by a downstream migration was only seen in 26% (n = 7) of fish, while 41% (n = 11) deviated from the paradigm and made multiple reversals and numerous movements on and off the spawning grounds. Oscillations spanned from the estuary into the reconnected habitat and resulted in a proportionally large amount of time spent in the estuarine and brackish habitats. Some oscillations also consisted of multiple fishway passage events within a season. Oscillation behavior is likely a naturally occurring spawning strategy that has gone undetected. Consequently, the proportion of individuals of a population that display single versus multiple passage events could result in fishway counts that bias run size estimations and thus population assessments.

Upstream fishway performance by Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) spawners at complex hydropower dams — is prior experience a success criterion?

Passage of hydropower plants by upstream-migrating salmonid spawners is associated with reduced migration success, and the need for knowledge of fish behavior downstream of dams is widely recognized. In this study, we examined fishway passage of landlocked Atlantic salmon (Salmo salar) in River Klarälven, Sweden, and brown trout (Salmo trutta) in River Gudbrandslågen, Norway, and the influence of prior experience on passage success in 2012 and 2013. Fishway trap efficiency varied from 18% to 88% and was influenced by river discharge. Most salmon (81%) entered the fishway trap on days without spill, and salmon moved from the turbine area to the spill zone when there was spill, with small individuals showing a stronger reaction than large fish. Analysis of fish with and without prior trap experience showed that a higher percentage of the “naïve” fish (70% of salmon and 43% of the trout) entered the fishway traps than the “experienced” ones (25% of the salmon and 15% of the trout). Delays for fish that entered the trap ranged from 3 to 70 days for salmon and 2 to 47 days for trout.

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

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

Fishway passage success for migratory rainbow smelt Osmerus mordax is not dictated by behavioural type

AbstractRecent research has demonstrated that an individual's behavioural decisions can have a profound impact on an animal's fitness. For anadromous fishes requiring access to spawning habitat above obstructions, successful passage at fishways may at least in part be a function of an individual's behavioural type. The objectives of this study were to determine whether distinct behavioural types—bold and shy—could be distinguished within a population of anadromous rainbow smelt (Osmerus mordax) and, if so, whether passage success at a nature‐like fishway varied relative to behavioural type. Field‐caught rainbow smelt were tested for individual differences in boldness (i.e., willingness to engage in risk‐taking behaviour) using the metrics of exploratory behaviour, general activity, and response to a simulated predator. After testing, 276 rainbow smelt were implanted with a passive integrated transponder tag, released below the fishway, and their movements monitored via a stationary antenna array. The results of our behavioural assays indicated the presence of a behavioural syndrome among rainbow smelt, and that behaviour was partially repeatable. In total, 41.7% of fish entering the fishway passed successfully, but contrary to our initial prediction, boldness was not a significant predictor of successful passage. Instead, increasing water temperature and decreasing river discharge were consistent predictors of successful passage and greater distances moved through the fishway. Our findings indicate that the nature‐like fishway did not select for a particular behavioural type and that individuals representing the spectrum of bold–shy behavioural types could pass.

Swimming activity and energetic costs of adult lake sturgeon during fishway passage.

Fish migrations through riverine systems can be energetically demanding, and the presence of fishways to facilitate upstream passage can add an additional energetic cost that may directly affect fitness. Successful fishway passage is a function of the ability of fish to select appropriate paths and swimming strategies that do not exceed their swimming capacity. Triaxial accelerometers were used to estimate the energetic expenditure of adult lake sturgeon (Acipenser fulvescens) swimming through a vertical slot fishway, to determine whether individual behaviour or path selection, resulting in differences in cumulative energy use, explain fishway passage success. Most individuals attempted to pass the fishway (n=30/44; 68%), although successful passage only occurred for a subset of those attempting (n=7/30; 23%). High-speed swimming was rarely observed during upstream passage through fishway basins, and was of short duration. Two turning basins delayed passage, subsequently resulting in a higher energetic cost. The rate at which energy was expended did not differ among successful and unsuccessful individuals, although successful sturgeon exhibited higher costs of transport (42.75 versus 25.85 J kg(-1) m(-1)). Energy expenditure metrics were not predictive of successful fishway passage, leading us to conclude that other endogenous or exogenous factors influence passage success. In a practical application of field measurements of energy expenditure, we demonstrate that fishway passage through a structure designed to facilitate migration does result in an energetic loss for lake sturgeon (3249-16,331 J kg(-1)), equivalent to individuals travelling 5.8-28.2 km in a lentic system.

How migrating lake sturgeon cope in fishways

Migrations have always been gruelling, from the Herculean flights of bar-headed geese to the epic odysseys of salmon returning upriver to their spawning grounds. However, when humans began altering river systems, taming them with dams, the channels of many migrating fish became utterly impassable. To mitigate the disruption, fish ladders – or fishways – are often installed to expedite the passage of migrating species. However, many of the current fishway designs are based on our understanding of a few poster-child species, such as the salmon, and few have considered the impact on other, less athletic species. ‘Sturgeons are one of the most threatened groups of fish in the world’, says Jason Thiem, from Carleton University, Canada, adding, ‘Little research has been conducted on fishway use by sturgeon, despite the recognition that barriers to migration represented a threat to the process’. With the future of these species in jeopardy, Thiem, Jeff Dawson and Steven Cooke decided to track the progress of lake sturgeon (Acipenser fulvescens) through a fishway to find out how much exertion the ungainly swimmers require to negotiate these obstacles.After selecting the Vianney-Legendre Fishway on Quebec's Richelieu River for their study with the help of sturgeon and fishway experts Pierre Dumont and Daniel Hatin, Thiem and colleagues had only a brief 2-week period to capture sturgeon as they congregated below the fishway, ready to negotiate the obstacle in a bid to swim upstream to spawn. ‘It took 3 years to get the right field conditions for us to be able to undertake this field study’, says Thiem, who recalls battling adverse conditions. Having previously drained the 85 m long channel and fitted 15 antennae at intervals along its course to track the fish's progress, the team then fitted electronic tags and accelerometers to 44 sturgeon to monitor their movements, before releasing the animals and recording their progress as they ascended the fishway.Retrieving the tags from the fish and releasing them at a spawning site, Thiem realised that although seven of the fish had successfully negotiated the 85 m channel – after as many as 16 attempts – 23 failed to reach the end and 14 never even attempted the climb. Calculating the fish's swimming speeds, the team discovered that most of the fish swam at relatively leisurely rates (≤1.25 m s−1); ‘We rarely observed high speed swimming and hyperactivity’, recalls Thiem. And when Thiem, Andy Danylchuk, Adrian Gleiss and Rory Wilson analysed the fish's energy consumption, there was little difference between the fish that succeeded in reaching the top and those that did not. However, the successful fish used more energy per meter (42.75 J kg–1 m–1) than the unsuccessful sturgeon (25.85 J kg–1 m–1). And when the team calculated the fishes’ energy consumption as they negotiated the two turns in the channel, they saw that the sturgeons’ cost of transport increased significantly. The team also compared the plucky sturgeons’ energy consumption as they tackled the ascent with the energy consumption of sturgeon swimming at similar speeds through a tranquil lake – their usual environment – and realised that as they repeatedly attempted to ascend the channel, the sturgeon consumed as much energy as sturgeon swimming 5.8–28.2 km in peaceful lakes.‘Swimming uphill is energetically demanding’, says Thiem, adding, ‘We expected sturgeon to be poor swimmers… [however,] this is not the case and swimming performance is unlikely to be a limiting factor in fishway passage success’. Thiem also adds that sturgeon would benefit enormously if fishways were redesigned and the turn structures removed. ‘We identified that the absence of turning basins in the current fishway design would reduce passage time and correspondingly reduce energy expenditure’, he says.

Evaluating the effectiveness of a Larinier super active baffle fish pass for European river lamprey Lampetra fluviatilis before and after modification with wall-mounted studded tiles

To help achieve effective longitudinal river connectivity, evaluation of the efficacy of fishway use by upstream-migrating fishes is needed. Larinier super active baffle (SAB) fishways are relatively cheap retrofit fish passes, suitable for low-head barriers, widespread in Europe and the most commonly fitted technical pass in Britain. Their suitability for non-salmonids, however, is poorly quantified. The efficacy of a 15% gradient SAB fishway and effects of flow regime and water temperature were tested for European river lamprey (Lampetra fluviatilis) using passive integrated transponder (PIT) and acoustic telemetry at a Crump weir on the River Derwent, Northeast England. In migration season 2013–14, over a wide range of flows, 90.1% of 350 tagged lamprey entered the fishway. One fish (0.3%) of those that entered the pass ascended successfully, even though measured water velocity was within laboratory-measured performance conditions for this species. Of 29 acoustic-tagged lamprey that visited the weir over the same period, four (13.8%) ascended it directly, during elevated flows. These data suggest that high turbulence and/or the physical characteristics of baffles may inhibit lamprey ascent of the pass. In migration season 2014–15, we tested the effect of adding studded modular plastic tiles adjacent to the fishway wall, employing PIT antennas separately interrogating the entrance and exit of each of the main fishway and tile routes. 85.8% (169) of 197 tagged lamprey entered the fishway, of which 72/169 (42.6%) entered the tile entrance. Passage efficiency of entrants was 7.1% (12/169), all of which used the tiled route. Reduced local flow velocity in combination with increased availability of resting habitat within the tiles may have facilitated increased passage. Although fishway passage efficiency increased after placement of the modular tiles, it remained half that measured for direct weir passage, both of which are inadequate for connectivity restoration. Quantitative tests of studded tiles placed on the sloping downstream weir face by comparison to control conditions may be more effective and are needed. This study demonstrates the importance of carrying out full-scale field tests to supplement possible solutions developed under laboratory conditions.

Fishway approach behaviour and passage of three redhorse species (Moxostoma anisurum, M. carinatum, and M. macrolepidotum) in the Richelieu River, Quebec

Fishways are increasingly constructed to maintain longitudinal connectivity for fish in numerous river systems where migrations are interrupted by anthropogenic barriers, although there is a paucity of information on the biological effectiveness of fishways for most species. We evaluated fishway approach behaviour, and quantified attraction and passage efficiency of three catostomid species (silver redhorse Moxostoma anisurum, river redhorse M. carinatum and shorthead redhorse M. macrolepidotum) that undertake annual obligate spawning migrations through the Vianney-Legendre vertical slot fishway at the St. Ours Dam, in the Richelieu River, Quebec, Canada. Use of PIT tagging alone enabled quantification of attraction and passage efficiency and these were; 51, 17 and 50 % for attraction efficiency and passage efficiencies were 88, 50, and 69 % for silver, river, and shorthead redhorse, respectively. Silver redhorse had significantly shorter entrance delay and passage duration times than shorthead redhorse. Attraction efficiency was different among release locations for silver redhorse, and passage efficiency increased with size for shorthead redhorse. For all species, failure to ascend the fishway was most likely to occur before the second turning basin (before the 32 m mark) in the fishway (84 % of failures). Silver redhorse had significantly lower passage failure rates than river and shorthead redhorse. Activity patterns in the three species during fishway passage were different; crepuscular activity patterns were observed in shorthead and river redhorse, whereas silver redhorse activity peaked between 23:00 and 02:00 then decreased through the remainder of the day. To further evaluate fishway approach behaviour we fitted an additional sample of each species with external radio tags, although nearly all radio tagged individuals (n = 119) rapidly moved downstream upon release immediately post-tagging. Subsequently, our results were confounded by the behavioural impairments associated with external radio tagging and fallback. These results demonstrate the value of multispecies fishway evaluations and highlight the variation among individual species fishway performance within a single genus.

To boldly climb: behavioural and cognitive differences in migrating European glass eels.

European eel (Anguilla anguilla) is a catadromous fish species that received substantial attention as its population has markedly declined in the last three decades. The possible causes of this decline include habitat fragmentation factors such as dams and weirs. In some cases, these obstacles are equipped with fish friendly passage devices that may select young eels according to their climbing behaviour. We tested how individual climbing tendency was related to the event of fishway passage experienced in the field and classified fish climbing profiles as climbing ‘leaders’, ‘followers’, ‘finishers’ and ‘no climbers’. Moreover, we analysed the brain transcription level of genes related to neurogenesis and synaptic plasticity and compared it to climbing profiles. We found that fish from the upstream segments of an impounded river had a higher climbing propensity. Their behaviour was also more repeatable throughout the whole test than the obstacle-naive fish from the downstream segment. Moreover, we found that boldly climbing ‘leaders’ had lower levels of transcription of synapse-related genes than the climbing ‘followers’. These differences could be related to coping styles of fish, where proactive ‘leaders’ express a routine and risky behaviour, whereas reactive fish need an environmental assessment before exploratory behaviour. Our study showed that differences in climbing propensity exist in glass eels separated by water obstacles. Moreover, eels could adopt climbing different strategies according to the way they deal with environmental stress and to the cognitive abilities they possess.

Behaviour and locomotor activity of a migratory catostomid during fishway passage.

Fishways have been developed to restore longitudinal connectivity in rivers. Despite their potential for aiding fish passage, fishways may represent a source of significant energetic expenditure for fish as they are highly turbulent environments. Nonetheless, our understanding of the physiological mechanisms underpinning fishway passage of fish is still limited. We examined swimming behaviour and activity of silver redhorse (Moxostoma anisurum) during its upriver spawning migration in a vertical slot fishway. We used an accelerometer-derived instantaneous activity metric (overall dynamic body acceleration) to estimate location-specific swimming activity. Silver redhorse demonstrated progressive increases in activity during upstream fishway passage. Moreover, location-specific passage duration decreased with an increasing number of passage attempts. Turning basins and the most upstream basin were found to delay fish passage. No relationship was found between basin-specific passage duration and activity and the respective values from previous basins. The results demonstrate that successful fishway passage requires periods of high activity. The resultant energetic expenditure may affect fitness, foraging behaviour and increase susceptibility to predation, compromising population sustainability. This study highlights the need to understand the physiological mechanisms underpinning fishway passage to improve future designs and interpretation of biological evaluations.

Fishway Bottleneck Relief Models: a Case Study using Radio‐Tagged Pacific Lampreys

AbstractStructural or operational changes to fishways can improve fish passage efficiency, but there is often uncertainty regarding which improvements will be most effective. We developed a “bottleneck relief” model using Kaplan–Meier methods to help managers assess where remediation efforts are likely to provide the largest increases in fishway passage. The simulation model uses a matrix of observed efficiency estimates from fishway subsections and incorporates multiple passage attempts by individual tagged fish. In a case study application to test the model, we used radiotelemetry data from 2,170 adult Pacific Lampreys Entosphenus tridentatus at Bonneville Dam (Columbia River, Washington–Oregon), which features multiple fishways and low lamprey passage success (mean fishway passage efficiency ∼0.50; n = 10 years). The model was run iteratively to test potential dam passage benefits from improving efficiency in 20 individual fishway segments. The highest benefits were for improvements at top‐of‐fishway segments and at sites where passage routes converged. Benefits were lower for segments used by fewer fish, segments located downstream from serious bottlenecks, and segments with a limited scope for improvement (i.e., efficiency was already high). The model provides a flexible and objective method for assessing complex fish passage problems and informing remediation decision making.Received December 19, 2013; accepted March 11, 2014

Fishway passage bottleneck identification and prioritization: a case study of Pacific lamprey at Bonneville Dam

Fishways designed for salmonids often restrict passage by non-salmonids, and effective tools are needed both to identify passage problems for nontarget species and to inform remediation planning. In this case study, we used migration histories from 2170 radio-tagged adult Pacific lamprey (Entosphenus tridentatus) to identify locations of poor passage (bottlenecks) at a large, multifishway dam. Over 10 years, 49% of tagged lamprey that entered fishways failed to pass the dam. Models accounting for repeated attempts by individual lamprey indicated successful passage strongly depended on attempted passage route. Success also varied with time of fishway entry, water temperature, and lamprey body size. Most failed passage attempts terminated in lower fishway segments, but extensive seasonal shifts in bottleneck locations were detected. Ranking metrics helped prioritize bottlenecks and identified sites where structural or operational modifications should improve lamprey passage. Our integration of spatially intensive monitoring with novel analytical techniques was critical to understanding the complex relationships among fishway features, environmental variation, and lamprey behavior. The prioritization framework can be applied to a wide range of fish passage assessments.

Comparative Physiology and Relative Swimming Performance of Three Redhorse (Moxostomaspp.) Species: Associations with Fishway Passage Success

Our understanding of biological criteria to inform fish passage design is limited, partially due to the lack of understanding of biological motivators, cues, and constraints, as well as a lack of biological performance evaluations of structures once they are built. The Vianney-Legendre vertical slot fishway on the Richelieu River, Quebec, Canada, passes large numbers of migrating redhorse (Moxostoma spp.) upriver to spawning grounds each year. We evaluated the physiological capacity and relative swimming ability of three redhorse species (Moxostoma anisurum, Moxostoma carinatum, Moxostoma macrolepidotum; silver, river, and shorthead redhorse, respectively) to determine how these biotic factors relate to variation in fishway passage success and duration. Shorthead redhorse had higher maximum metabolic rates and were faster swimmers than silver and river redhorse at their species-specific peak migration temperatures. Blood lactate and glucose concentrations recovered more quickly for river redhorse than for silver and shorthead redhorse, and river redhorse placed second in terms of metabolic recovery and swim speed. Interestingly, fish sampled from the top of the fishway had nearly identical lactate, glucose, and pH values compared to control fish. Using passive integrated transponders in 2010 and 2012, we observed that passage success and duration were highly variable among redhorse species and were not consistent among years, suggesting that other factors such as water temperature and river flows may modulate passage success. Clearly, additional research is needed to understand how organismal performance, environmental conditions, and other factors (including abundance of conspecifics and other comigrants) interact with fishway features to dictate which fish will be successful and to inform research of future fishways. Our research suggests that there may be an opportunity for a rapid assessment approach where fish chased to exhaustion to determine maximal values of physiological disturbance are compared to fish sampled from the top of the fishway, which could reveal which species (or sizes of fish) are approaching or exceeding their physiological capacity during passage.

Fishway passage and post‐passage mortality of up‐river migrating sockeye salmon in the Seton River, British Columbia

AbstractAdult sockeye salmon (Oncorhynchus nerka) were studied to assess the consequences of a dam and vertical‐slot fishway on mortality during their spawning migration in the Seton–Anderson watershed, British Columbia, Canada. Since previous research suggests fishway passage may be difficult, our main hypothesis was that the dam and fishway have post‐passage consequences that affect subsequent behaviour and survival. Eighty‐seven sockeye were caught at the top of the fishway, implanted with an acoustic telemetry transmitter, non‐lethally biopsied to obtain a small blood sample and released either upstream or downstream of the dam. Indices of physiological stress (i.e. plasma cortisol, glucose, lactate and ions) indicated that fish were not stressed or exhausted after capture from the fishway, and were not unduly stressed by transportation to release sites or net‐pen holding. Of 59 fish released downstream of the dam, 14% did not reach the dam tailrace. Overall passage efficiency at the fishway was 80%. Mortality in two lakes upstream of the dam was greater in fish released downstream of the dam (27%) compared to fish released upstream of the dam (7%; p = 0.04) suggesting that dam passage has consequences that reduce subsequent survival. Cumulative mortality of fish released downstream of the dam (n = 55) resulted in only 49% survival to spawning areas, compared to 93% of fish released upstream of the dam (n = 28). Survival was significantly lower for females (40%) than for males (71%; p = 0.03), a finding that has implications for conservation because spawning success of sockeye salmon populations is governed primarily by females. Copyright © 2010 John Wiley & Sons, Ltd.

Swimming Performance and Fishway Model Passage Success of Rio Grande Silvery Minnow

AbstractWe used a swim chamber, flume, and large‐scale fishway models to assess the swimming performance, behavior, and passage success of endangered Rio Grande silvery minnow Hybognathus amarus. Field‐captured silvery minnow (53–88 mm total length) swam 114–118 cm/s (i.e., up to 20.9 body lengths/s) in a swim chamber in water temperatures of 15, 19, and 23°C. The relationship between time to fatigue and water velocity showed that endurance declined sharply at velocities above 60 cm/s, a threshold that is consistent with critical swimming speed estimates and may represent a transition from aerobic to anaerobic metabolism. Water temperature and fish length were positively correlated with swimming performance. At water velocities of 60 cm/s and less, silvery minnow routinely swam the equivalent of 50 km (125 km maximum) in a swim chamber in less than 72 h. The proportions of silvery minnow that successfully ascended a flume over sand, gravel, or cobble substrate declined as water velocity increased to 53 cm/s. Passage times increased at higher water velocities and at a faster rate over sand substrate because fish were stationary for longer periods over the lower‐velocity boundary layers created by gravel and cobble at all velocities. Dual‐vertical‐slot fishway passage was 52% in a less turbulent flow of 78 cm/s; passage was 8% at a faster, more turbulent flow of 87 cm/s. Conversely, 75% of silvery minnow ascended a rock channel fishway with a holding pool present and a 1% hydraulic gradient in low (58‐cm/s) and high (83‐cm/s) mean flow velocities. Differences in willingness to swim, longer test duration, and the mosaic of water velocities created by the bed roughness elements may explain the higher silvery minnow passage success in the rock channel. Predictive swimming fatigue relationships, together with fish length and water temperature, may guide decisions regarding fishway lengths and velocities so as to permit passage of Rio Grande silvery minnow.

A Comparison of the Physiological Condition, and Fishway Passage Time and Success of Migrant Adult Sockeye Salmon at Seton River Dam, British Columbia, under Three Operational Water Discharge Rates

AbstractWe investigated the effect of changes in water discharge from the Seton River Dam, British Columbia, on the physiological condition, passage time, and passage success of adult migrant sockeye salmon Oncorhynchus nerka. Sockeye salmon were intercepted and nonlethally biopsied for blood plasma and energy status. A subset of these fish were fitted with radio transmitters and tracked under three different operational attraction flow levels. Indices of physiological stress and exhaustive exercise (e.g., plasma cortisol, glucose, lactate, osmolality, and hematocrit) did not differ among the attraction flow discharge levels that were examined, nor did they differ appreciably from those of other adult Fraser River sockeye salmon studied during upriver migrations in areas of natural, nonregulated flows. In fact, the fish appeared relatively unstressed after dam passage. Passage time was significantly longer (19.9 h) under intermediate discharge (12.7 m3/s) than under high (15.8 m3/s) or low (11.0 m3/s) discharges (9.3 and 7.0 h, respectively) but did not differ between high‐ and low‐discharge periods. No differences in passage success or fishway ascent time were observed among the three discharges. Though we suspect that unique flow conditions were responsible for the longer passage time during intermediate discharge, a detailed hydraulic analysis is needed to further interpret our results.