Denil Fishways Research Articles

Comparative Biotic Monitoring of a Modified Denil Fishway and a Pool and Weir Fishway on a Small Tributary in the Upper Trout Region

Modified Denil fishways have a centred gabion containing gravel and are intended to enable the free passage of riverbed-oriented species and invertebrates. An experimental plant was built at a small hydropower station which provided a newly arranged Denil fishway and a pool and weir fishway parallel to one another. It was possible to alternately operate the systems for monitoring purposes owing to the parallel design, allowing an appropriate comparison and analysis of the results to be carried out. The primary objective of this study is to qualitatively and quantitatively compare the size selectivity and ascent numbers between the new development and the conventional construction type. An important component of this study is the test to prove the passage of bullheads in the modified Denil fishway using an experimental set-up. The results of this study depict a similar size distribution of ascended fish in both construction types and thus provide no evidence of selectivity for small fish sizes. Likewise, no deficit of the modified Denil fishway compared with the pool and weir fishway could be proven within the scope of a monitoring. The successful passage of bullheads could be demonstrated in the experiment as well as during monitoring.

Passage Efficiency of Alewife in a Denil Fishway Using Passive Integrated Transponder Tags

AbstractPopulations of river herring (Alewife Alosa Pseudoharengus and Blueback Herring A. aestivalis, collectively), once abundant in coastal rivers along the Atlantic coast, have seen precipitous population declines, likely due to many factors, including commercial fishing, habitat degradation, and dam construction. Efforts to restore populations include the construction of fishways at dams, but upstream passage success of fish through fishways is variable. To evaluate passage efficiency of a fishway on the Lamprey River in Newmarket, New Hampshire, Alewives were PIT tagged in 2013 (n = 621) and 2014 (n = 501) and antennas monitored fish in 2013–2015. Potential handling effects, diel movement patterns, and fishway saturation negatively affected passage success. The probability of Alewives successfully passing through the fishway into the river above the dam increased with total length. The estimated probability of passage success of an Alewife of mean total length (280 mm and 292 mm for males and females, respectively) that migrated back to the dam at least 1 year after tagging was 0.63 for males and 0.64 for females. Fishway selectivity presents a potential bias in data collection in freshwater systems, and our results suggest that sampling below a fishway should be coupled with data collected from within and above the fishway for a more complete demographic sample of the migratory population.

Flow-Control Plates to Manage Denil Fishways in Irrigation Diversions for Upstream Passage of Arctic Grayling

Abstract Small-stream irrigation diversions are key elements of many on-farm irrigation systems but can act as barriers to aquatic species. Denil fishways have been installed at irrigation diversion structures throughout the Big Hole River watershed in Montana to provide upstream passage for a population of Arctic Grayling Thymallus arcticus. When stream flows are low and irrigation demand is high, irrigators look for ways to maintain adequate diversion, but doing so may reduce the effectiveness of the fishways. In response, agencies and irrigators have proposed flow-control plates placed at the upstream end of fishways. We conducted laboratory-based fishway efficiency experiments with Arctic Grayling placed in an open-channel flume fitted with a Denil fishway and three flow plates. Of the total 200 fish that we used, the fishway entrance attracted 154 fish and we counted these fish as participants. We operated the fishway under varying flow conditions using three flow-control plate treatments and a control to investigate 1) the extent to which each treatment reduced flow compared to the control, and 2) the extent to which each treatment impacted passage success of Arctic Grayling relative to the control. We measured passage success as the ratio of the number of fish that fully ascended the fishway treatment to the number of participant fish attracted to the fishway treatment. One of the three plates, the Denil slot treatment, showed no evidence of reducing either flow or passage success. Another plate, the standard treatment, showed no evidence of reducing flow but moderate evidence of reducing passage success (P = 0.03). The only treatment to significantly reduce water flow rate was the narrowed Denil slot treatment and there was no evidence this treatment reduced passage in comparison to the control. Over all trials, water flow rate through the Denil fishway had a strong positive influence on fish passage success.

A scaled Denil fishway for upstream passage of Arctic Grayling

Denil fishways have been used with varying success to help fish pass impediments to upstream passage such as low head dams or irrigation diversion structures. They have been tested for hydraulic and fish passage performance in laboratory and field settings, usually with only minor modifications to the fishway geometry or dimensions. We tested a reduced (0.6) scale prototype of the standard-sized Denil fishway to determine if the smaller fishway, which requires less water flow, would successfully pass Arctic Grayling (Thymallus arcticus). The scaling factor was informed by analyzing previously published scalable Denil fishway rating equations. A prototype was tested in an open-channel flume using 8 treatments with 3 trials per treatment and 8 fish per trial. Each treatment had a prescribed combination of headwater and tailwater depths. Overall, 93% (178/191) of the fish volitionally entered the fishway and of these 91% (162/178) passed successfully. Entrance and passage were reduced only in treatments with the highest hydraulic slopes and highest water velocities at the downstream end of the fishway (i.e. with high headwater depths and low tailwater depths). The 0.6-scaled Denil fishway is likely a good alternative to standard-sized Denil fishways to enhance upstream mobility of Arctic Grayling in small, water-limited streams.

Attraction, Entrance, and Passage Efficiency of Arctic Grayling, Trout, and Suckers at Denil Fishways in the Big Hole River Basin, Montana

AbstractThe Big Hole River basin in southwestern Montana supports the only indigenous, self‐sustaining fluvial population of Arctic Grayling Thymallus arcticus in the conterminous United States, but the basin is fragmented by numerous low‐head irrigation diversion dams. Denil fishways at 63 diversion dams provide Arctic Grayling and other fishes opportunities for year‐round access to critical habitats; however, their efficiency has not been evaluated. We quantified attraction, entrance, and passage for hatchery‐reared Arctic Grayling, wild trout (Brook Trout Salvelinus fontinalis and Brown Trout Salmo trutta), and wild suckers (White Sucker Catostomus commersonii and Longnose Sucker C. catostomus) during 14 field trials conducted at six Denil fishways over a representative range of fishway slopes and hydraulic conditions using passive integrated transponder telemetry. Attraction (60.4–84.3%) and entrance (44.3–78.6%) efficiencies were variable across test conditions and reduced overall fishway efficiencies (19.1–55.8%). In contrast, upon entry, passage efficiencies were high (96.2–97.0%) for all taxa across all test conditions. Attraction of hatchery‐reared Arctic Grayling increased with upstream depth (a surrogate for fishway discharge) and attraction flow, but attraction of wild fish was less affected by these conditions. Entrance of Arctic Grayling, Brook Trout, and Brown Trout decreased with upstream depth and fishway slope, especially when plunging entrance conditions associated with shallow downstream depths were present. However, entrance of Arctic Grayling and both trout species increased with downstream depth, and submerged fishway entrances demonstrated promise for increasing entrance efficiency at fishways with high discharges and steep slopes. We demonstrate that comprehensive evaluations of fishway efficiency components can identify specific solutions that improve fishway efficiency; application of these engineering solutions at individual fishways (as needed) could improve their efficiency and further enhance aquatic connectivity for fishes in the Big Hole River basin and elsewhere.

The effect of water depth on passage success of arctic grayling through two Denil fishways

Arctic grayling (Thymallus arcticus) are found throughout parts of North America, Europe and Asia. Denil fishways are being used in efforts to recover populations and provide passage for grayling through water diversions in Montana and elsewhere. This study evaluated how water depths in 1.83 m and 3.66 m Denil fishways affect upstream passage for grayling. The study was performed in a laboratory at the Bozeman Fish Technology Center (BFTC) in Bozeman, MT. Fifteen passage trials of different treatment combinations of approach depth and sill depth were performed in each ladder. A total of 310 grayling, in groups of 10 per trial, were allowed to volitionally attempt to swim upstream through each ladder. For the 1.83 m Denil, 81 of 137 participants successfully ascended resulting in an overall passage of 59.1% among all trials compared to 82 of 147 participants successfully ascending the longer structure for an overall passage of 55.8%. A quasi-binomial regression model was used to predict passage success for different combinations of approach and sill depths. Our study showed upstream passage success increased with deeper water depths at the sill for both ladders with the exception of the configuration with the shallowest approach depth and deepest water depth at the sill.

Derivation and application of the energy dissipation factor in the design of fishways

Reducing turbulence and associated air entrainment is generally considered advantageous in the engineering design of fish passage facilities. The well-known energy dissipation factor, or EDF, correlates with observations of the phenomena. However, inconsistencies in EDF forms exist and the bases for volumetric energy dissipation rate criteria are often misunderstood. A comprehensive survey of EDF criteria is presented. Clarity in the application of the EDF and resolutions to these inconsistencies are provided through formal derivations; it is demonstrated that kinetic energy represents only 1/3 of the total energy input for the special case of a broad-crested weir. Specific errors in published design manuals are identified and resolved. New, fundamentally sound, design equations for culvert outlet pools and standard Denil Fishway resting pools are developed. The findings underscore the utility of EDF equations, demonstrate the transferability of volumetric energy dissipation rates, and provide a foundation for future refinement of component-, species-, and life-stage-specific EDF criteria.

Extreme inefficiency of two conventional, technical fishways used by European river lamprey (Lampetra fluviatilis)

In recent years, fishways have increasingly been designed and installed with the intention to not only provide economically important fishes, such as salmonids, with free passage at barriers, but also for other elements of the migratory fish community. However, in Europe and North America, large numbers of conventional technical fishways exist, for which the efficacy and suitability for non-salmonid species is often inadequately known. Using passive integrated transponder (PIT) telemetry, this study evaluated the efficacy of two such conventional, technical fishways (pool and weir and plain Denil baffle) located on the Yorkshire River Derwent, north-east England, for the threatened anadromous European river lamprey Lampetra fluviatilis, an anguilliform swimmer, over the upstream migration and spawning seasons. For lamprey that entered the fishways, 0.0% and 5.0% passage efficiencies were recorded for Denil (n=1) and pool and weir (n=1) fishways, respectively, over the entire study period. The pool and weir fishway exhibited poor attraction efficiency (42.6%) compared to the Denil fishway (91.8%), and lamprey took significantly longer to locate the pool and weir fishway, probably as a result of ineffective attraction flow. Most lamprey detected at the fishway entrances were recorded within 24h of release and returned mostly during high flow events on up to 12 separate dates over a 150 day period. Under these conditions, these fishways were unsuitable for river lamprey. Emphasis is placed upon the increased need for a thorough consideration of the entire migratory fish community during the inception of fishway designs, and that post-construction, strategic evaluation of fishways should be actively supported and encouraged to advance the provision of effective multi-species fishways.

Hydrodynamic Characteristics in Ecological Arc-Shaped Baffle Fishway

Fishways are hydraulic structures allowing fishes upstream migration through engineering constructions in the rivers. The Denil type has a wide application and the main components are flat baffles. In this paper, we present a new type of baffle (arc-shaped baffle) to ameliorate the hydrodynamic characteristics in the fishway. The main improvement of arc-shaped baffle fishway is the alteration that the flat baffles are replaced by arc-baffles. In order to investigate the influence of water flow on migratory fish in the arc-baffle fishway, model tests were conducted. Based on the experimental results, the conclusion can be reached that hydrodynamic characteristics in arc-shaped baffle fishways are steadier than that in traditional Denil fishways, which makes fishes ascend easily.

Hydromechanical Analysis of Desilting Mechanism of Ecological Arc-Shaped Baffle Fishway

In this paper, we developed a new type of ecological Denil fishway installed with arc-shaped baffles which can split upstream flow to improve the flow condition for fish migration. In fact, the arc-shaped is based on architectonics theory and imitate the mechanism of architectonics.So it has good effectiveness. During the construction course, building materials can be used to improve efficiency.By setting water flow orifices near the V-shaped notch, the energy dissipation can be increased as result of the interaction between the water from the orifices and the water from the notch. The sand or other sediments accumulated on the fishway floor can be washed away by the flow through desilting orifices, meeting the requirement of purificating the fishway and providing a clear environment for fish species. Model tests were conducted to investigate the desilting capability of the ecological arc-shaped baffle fishway and the results agree well with the hydromechanical analysis.

Optimising Denil fishways for passage of small and large fishes

Abstract An 8‐m long experimental fishway was trialled at three different slopes [8.3% (1:12), 14.3% (1:7) and 20% (1:5)] to examine the potential of the single‐plane Denil fishway for the passage of small‐ and large‐bodied native fishes in Australia. Fish between 45 and 630 mm ascended the fishway. The lowest slope enabled the full size range of bony herring Nematalosa erebi (Günther), from 45 to 350 mm fork length, to ascend the fishway successfully as well as a higher numerical proportion; 88% at the 8.3% slope compared with 31% at the 20% slope (fish numbers per trial = 33–3936). These results dispel the notion that Denil fishways are inherently poor for small fishes. Manipulating the design parameters of slope, length, width and possibly depth‐over‐breadth ratio enables Denil fishways to pass a wide size range of fish, which may greatly extend their present application and enable them to make a greater contribution to the rehabilitation of diverse fish communities.

Discharge Rating Equation and Hydraulic Characteristics of Standard Denil Fishways

This paper introduces a new equation to predict discharge capacity in the commonly used Denil fishway using water surface elevation in the upstream reservoir and fishway width and slope as the independent variables. A dimensionless discharge coefficient based only on the physical slope of the fishway is introduced. The discharge equation is based on flow physics, dimensional analysis, and experiments with three full-scale fishways of different sizes. Hydraulic characteristics of flow inside these fishways are discussed. Water velocities decreased by more than 50% and remained relatively unchanged in the fully developed flow downstream of the vena contracta region, near the upstream baffle where fish exit the fishway. Engineers and biologists need to be aware of this fact and ensure that fish can negotiate the vena contracta velocities rather than velocities within the developed flow region only. Discharge capacity was directly proportional to the fishway width and slope. The new equation is a design tool for engineers and field biologists, especially when designing a fishway based on flow availability in conjunction with the swimming capabilities of target fish species.

Denil fishway utilization patterns and passage of several warmwater species relative to seasonal, thermal and hydraulic dynamics

Abstract – Two different Denil fishways on the Grand River, Ontario, were used as check‐points to evaluate the upstream movement of fishes past a low‐head weir and to examine the proportions and inferred swimming performance of non‐salmonid warmwater fishes that used each fishway type. Traps installed at fishway exits were used to collect fish during 24‐hour sampling periods, over 40–51 days each year, from 1995 to 1997. Passage rates, size selectivity, water temperature, water velocity and turbidity for the periods of maximum passage for each year were examined. General species composition from trap samples shifted from catostomids to cyprinids to ictalurids to percids and centrarchids, with some overlap, as water temperatures increased from 8 °C to 25 °C in the spring and early summer. Water depths, and therefore water velocities in each fishway, were independent of river discharge due to variable accumulations of debris on upstream trash‐racks. Relationships between the water velocity and the swimming and position‐holding abilities of several species emerged. Turbidity was directly related to river discharge and precipitation events, and many species demonstrated maximum fishway use during periods of increased turbidity. This study 1) provided evidence of strongly directional upstream movements among several species that were previously considered non‐migratory and 2) describes physical and hydraulic conditions during fishway use for 29 non‐salmonid fish species.

Fishway entrance modifications enhance fish attraction

Two Denil fishways on the Grand River, Ontario, were monitored annually since 1994 for activity by several dozen fish species. Fishway entrances were enlarged and repositioned approximately 2 m closer to the weir face, in areas where fish were attracted by weir discharge. These simple modifications resulted in increased attraction efficiency for pumpkinseed, Lepomis gibbosus (L.). After modifications, annual relative rate of recapture was 39% (95% confidence interval [CI]=32–46%), representing a 2.6–3‐fold increase in fishway use relative to pre‐modification conditions. Median daily recapture rates also increased significantly from 0% at both fishways to approximately 2%. These results suggest that fishway entrances should be located as close to a dam or weir face as possible, but velocity barriers from spillway or tailrace discharge must not compromise access.

Assessment of the Dunnville Fishway for Passage of Walleyes from Lake Erie to the Grand River, Ontario

A Denil fishway in Dunnville, Ontario was built to provide upstream passage for walleyes ( Stizostedion vitreum) from Lake Erie to the Grand River. Few walleyes have been observed to use this fishway. Coded radiotelemetry was used to track 24 adult walleyes (12 male, 12 female) downstream from the fishway to explore reasons for limited use. Activity was monitored by a fixed array of three antennas within the fishway that continuously scanned for signals from all radio-tagged fish, and by mobile tracking. In April and May 1997, 17 attempts to use the fishway by 3 male and 2 female radiotagged walleyes were recorded. During this period, the attraction efficiency of the Dunnville Fishway was approximately 21%. All attempts took place between 1600 and 0600 hours, with most activity near midnight. Walleyes occupied the first resting pool of the fishway for up to 17 h. Subsurface water velocity during the study was approximately 2 m/s. No radio-tagged walleyes passed through the Dunnville Fishway. Behavior modifying hydraulic conditions including turbulence, entrained air, backcurrents and whirlpools in fishway resting areas may delay or prevent successful upstream passage of walleyes. There was also evidence of large-scale movements by walleyes that may have spawned in the Grand River downstream from Dunnville.

Attraction and Passage Efficiency of White Suckers and Smallmouth Bass by Two Denil Fishways

We compared two Denil fishways, located on the west (low velocity, 10% slope) and east (high velocity, 20% slope) sides of the Mannheim weir, Grand River, Ontario, for use by upstream-migrating white suckers Catostomus commersoni and smallmouth bass Micropterus dolomieu. Mark–recapture and radiotelemetry were used to assess attraction and fish passage. Movement of 85 radio-tagged fish was monitored continuously during spring and early summer of 1995 and 1996. Attraction and passage efficiencies of white suckers at the west fishway were approximately 50%, and 55%, respectively. Attraction efficiency of white suckers at the east fishway was approximately 59%, and passage efficiency was 38%. The attraction and passage efficiencies of smallmouth bass at the west fishway were approximately 82% and 36%, respectively. At the east fishway, attraction efficiency of smallmouth bass was approximately 55%, and passage efficiency was 33%. There was an exponential decline in the numbers of both species that used each fishway relative to water velocity. The maximum water velocity used by white suckers was 0.96 m/s and that used by smallmouth bass was 0.99 m/s. Distracting flows near the west fishway appeared to affect attraction. Both fishways passed equal numbers of smallmouth bass per year, and smallmouth bass that used the east fishway were significantly larger than individuals that used the west fishway. In contrast, more than twice as many white suckers used the west fishway, and these fish were significantly larger than those that used the east fishway. Differences in passage were related to burst and critical swimming speeds and the use of velocity refugia within the fishways.

Effect of Slope and Headpond on Passage of American Shad and Blueback Herring through Simple Denil and Deepened Alaska Steeppass Fishways

Abstract Passage and transit time of adult upstream-migrant American shad Alosa sapidissima and blueback herring A. aestivalis were investigated in standard Denil and Alaska steeppass fishways with variable slope and headpond under semicontrolled conditions. Percent of American shad passed per unit time (percent passage) increased with temperature, while time required to ascend from the fishway entrance to the exit (transit time) decreased with increasing temperature for both species. Increasing fishway slope decreased percent passage of American shad, regardless of fishway type. Higher fishway slope decreased percent passage of blueback herring in the steeppass fishway only. Low headpond enhanced percent passage of American shad in the Denil fishway, but decreased percent passage of American shad in the steeppass fishway. Headpond level had no effect on percent passage of blueback herring in either fishway. Because headpond level in the steeppass fishway affected percent passage of American shad but not ...

Creation and maintenance of habitat downstream from a weir for the greenside darter, Etheostoma blennioides – a rare fish in Canada

The biology, microhabitat use and migratory behaviour of the greenside darter, Etheostoma blennioides, was studied at the Mannheim Weir on the Grand River, Ontario during the summer of 1995 and 1996. Officially listed as vulnerable in Canada, greenside darters reached maturity at age 1 and lived up to 4 years. They were found in riffle habitats that consisted of cobble and loose boulders, with large mats of Cladophora. This type of unembedded substrate is uncommon in the Grand River watershed. However, local abundance of greenside darters immediately downstream from the Mannheim Weir was likely due to high water velocities from weir discharge, freshets and ice scour which help maintain unembedded riffle areas. Trap data indicated that greenside darters temporally partition this habitat with the stonecat, Noturus flavus. Other darter species were not commonly found in areas with greenside darters, whose depth selection and habitat choices were influenced by predators and morphology. Denil fishways at the Mannheim Weir rarely passed greenside darters due to prohibitively high water velocities and exclusion by larger fish.

MIGRATORY BEHAVIOR OF JUVENILE AYU RELATED TO FLOW FIELDS IN DENIL AND STEEPPASS FISHWAYS

Portable Denil and steeppass fishways (0.3m wide, 0.3m deep) were experimentally installed on a divergent weir in Okitsu river. For ascended fishes to exit of the fishways, the number of fish in Denil were six times as many as ones in steeppass and the mean body size in steeppass were greater than ones in Denil. The fishes tend to choose the region of weak secondary flow and to ascend in upward secondary flow more than downward one in steeppass that contain much air bubble. The Denil fishways have the advantage of slower flow region without air bubbles for small fishes. It is pointed out for the juvenile ayu that flow directionality related to secondary flow and vortex scale have an effect on ascending behavior in the fishways.

Denil Fishways of Varying Geometry

This paper presents the results of an extensive laboratory study aimed at improving the design of Denil fishways. For the standard design of the simple Denil, an equation has been developed between the dimensionless discharge Q* and the relative depth of flow d/b for d/b as large as 5.5. The normalized velocity distributions in the centerplane of the Denil were found to have certain shapes depending upon the d/b ratio. For the nonstandard designs of the Denil fishway, based on the results of about 660 experiments, a method has been found to predict not only the relation between Q* and d/b but also the normalized velocity profiles in the centerplane of the Denil. The coefficient of friction between the central stream in the Denil and the circulating water on the sides as well as the bottom has been evaluated along with the equivalent Manning's n for the Denil fishway. These results are believed to be important in extending the depth range of the standard Denils as well as making changes to the standard Den...