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—The Smiths Fork, a tributary to the Bear River in western Wyoming, and the irrigation canals that form the Covey Canal system. Fish populations were estimated in 2003 at both random and congregated sites in the sections of the Covey Canal (Covey 1, 2, and 3), Spring Creek (SP), and the Mau Canal (Mau 1 and 2) delineated by bars.
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Irrigation canals can be a major source of mortality for fish in the Rocky Mountain region. Our study looked at how fish were affected by the irrigation canal system in the Smiths Fork, a tributary to the Bear River in western Wyoming. There are two native species of conservation concern in the Smiths Fork drainage: Bonneville cutthroat trout Oncor...
Citations
... large impact on fauna and flora in the basin from which the withdrawal occurred by destroying physical habitat (Winemiller & Anderson, 2008), dewatering rivers (Bauer et al., 2015;Rahel, 2013), entraining and impinging fishes (Lewis & Seegert, 2000), and serving as population sinks (Roberts & Rahel, 2008). ...
Water diversions worldwide may entrain or impinge fish and have population‐level impacts, but barriers like fish screens can reduce such threats. Traditional barriers are ineffective in the San Juan River, USA, due to high sediment and debris loads, so the Hogback Diversion Canal, NM, employs a novel weir wall design to reduce entrainment of sub‐adult and adult fishes. We evaluated the effectiveness of the weir wall in reducing the entrainment of larval fish using a combination of experimental and overnight trials. Larval fish densities were compared between the irrigation canal that delivers water to irrigators and subsequently entrains fish and the bypass canal that conveys water and fish back to the river. The density of hatchery‐produced larval fish collected in the irrigation canal during the experimental trial (0.74 fish/m ³ ) was 52% of their density in the bypass canal (1.43 fish/m ³ ), suggesting entrainment reduction. The density of wild‐produced larvae during overnight trials indicated some minor, mostly nonsignificant, differences between catch rates in irrigation and bypass canals, ontogenetic phases, and sampling dates. Though entrainment rates of wild‐produced larvae were not significantly reduced, density differences among postflexion mesolarvae and metalarvae suggest possible entrainment reduction of more developed ontogenetic phases. More intensive research is necessary to better elucidate the efficacy of the novel weir wall for reducing the entrainment of larval fish. However, our larval fish results and the results from prior large‐bodied entrainment studies suggest the novel weir wall may reduce fish entrainment in water diversions and benefit fluvial ecosystems in which traditional screens are unfeasible.
... These waterways provide direct (dispersal) or indirect (shipping) transportation routes for non-indigenous species, including planktonic organisms (Dexter et al., 2020). Some studies report that large rivers connected with canals differ in terms of hydrological and environmental characteristics, which influence the diversity of aquatic biota such as zooplankton species (Appel et al., 2020;Kelly et al., 2013;Ball et al., 2018), phytoplankton species (Dembowska, 2021;Kelly and Hassall, 2018), macrophytes (Tarkowska-Kukuryk and Grzywna, 2022;Dorotovičová, 2013), benthic invertebrates (McCabe et al., 1998;Weber et al., 2017) and fish (Chester and Robson, 2013;Onikura, 2015;Roberts and Rahel, 2008). The water flow velocity near locks determines the reproductive success of aquatic organisms and consequently influences growing potential. ...
... If diversion channels retain water, the conditions are often unsuitable for native fish spawning, recruitment and growth. Both the fish that perish and the ones that are left stranded in irrigation channels are lost from river populations (Prince, 1923;King & O'Connor, 2007;Roberts & Rahel, 2008;Baumgartner et al., 2009;Rahel, 2013) because gravity-fed irrigation channels often have a regulating structure limiting the movement of fish back into the main habitat. Thus, water diversion impacts are cumulative across many diversion points, resulting in losses that adversely affect native fish populations (King & O'Connor, 2007;Gale, Zale & Clancy, 2008;Killgore et al., 2023). ...
... Further investigation of the entrainment risks associated with different depths and behaviour of fish species is needed to provide a more detailed insight into the T A B L E 3 Total numbers caught and size (SL*) of measured fish caught in the Cohuna No. 3 irrigation channel. Fish protection screens at offtakes can influence fish assemblages and lead to possible fish community changes in irrigation channels (Cowley, Wissmar & Sallenave, 2007;Roberts & Rahel, 2008). The species diversity in most channels is lower than in the main river habitat, caused by conditions such as high variability of flow (Coates, 1984;Baumgartner, 2005), water management practices (dewatering), low food availability (Legner & Murray, 1981), relatively large short-term temperature variations, higher vulnerability for predation (King & O'Connor, 2007) or erosion and possible inputs from agricultural substances such as chemicals (Hamel, 2001;Baumgartner, 2005). ...
Each year, millions of fish are extracted from Australian waterways by the pumping and diversion of water into irrigation systems. Fish protection screens can help reduce these losses but are largely untested in Australian rivers.
In this study, a large, gravity‐fed irrigation offtake on Gunbower Creek, Victoria, Australia, was investigated for fish and debris entrainment. Experiments were performed under screened and unscreened conditions across various river flows.
Mark–release–recapture experiments were undertaken with fingerlings of two recreationally significant fish species, Murray cod ( Maccullochella peelii ) and golden perch ( Macquaria ambigua ), together with wild fish community assessments, to determine how effective the screen was at reducing fish entrainment into the irrigation channel.
The mean percentage of recaptured fingerlings was significantly lower when the irrigation channel offtake was screened compared with unscreened. Entrainment of released fish into the irrigation channel was reduced by >98%.
Similarly, wild fish entrainment was significantly lower when the irrigation channel was screened. When screened, fewer wild species dominated the sampled fish community, and entrained fish were generally <40 mm in length.
Debris loads decreased significantly in the irrigation channel owing to the screen, indicating the economic benefits of fish screens.
Implementing screens could aid in native fish conservation efforts in riverine environments.
... The large species richness of streams and canals is only partly accounted for by the large number of localities within these types. Small water currents serve as sink habitats for macroscopic (Roberts and Rahel 2008) as well as microscopic organisms (Bolgovics et al. 2017, Borics et al. 2021. They are connected with various other aquatic habitats of the watershed, and, because of their small size, microflora of the incoming waters considerably increases their diversity (Borics et al. 2015). ...
Climate change and human-induced habitat degradations result in loss of species diversity in natural ecosystems. While the extinction of macroscopic organisms has been well documented in both the scientific literature and the public media, we have only limited knowledge on the loss of microscopic elements of the ecosystems. Since rarity coincides with the increased risk of extinction, we investigated the commonness and rarity of microalgae in the Pannonian ecoregion. We reviewed the published literature of microalgal research in Hungary over the last 140 years and created a species-by-site matrix containing 2489 algae species and 1145 localities. Analysing this dataset, we found that although the core-satellite hypothesis suggests a bimodal site occupancy distribution, microalgae displayed a unimodal pattern with high number of rarely occurring species. We also demonstrated that the well-known negative relationship between the body size of organisms and the number of occupied habitats also holds for microalgae. Rarity values of taxa have a phylogenetic signal indicating that in terms of rarity, closely related species (desmids, dinoflagellates, euglenophytes) show considerable similarities. The various habitat types showed differences in the number of rare taxa. Small and medium-sized habitats (bog lakes, streams, oxbows) hosted the majority of rare species. These results highlight the conservation importance of small habitats in preserving microbial diversity.
... Previous studies have focused on water infrastructure as a sink habitat for fishes, where entrained fish experience high levels of mortality (Vinyard 1996;Gale et al. 2008;Roberts and Rahel 2008). Low densities of cutthroat trout in Grand Ditch align with these observations. ...
Interbasin water transfers are becoming an increasingly common tool to satisfy municipal and agricultural water demand, but their impacts on movement and gene flow of aquatic organisms are poorly understood. The Grand Ditch is an interbasin water transfer that diverts water from tributaries of the upper Colorado River on the west side of the Continental Divide to the upper Cache la Poudre River on the east side of the Continental Divide. We used single nucleotide polymorphisms to characterize population genetic structure in cutthroat trout (Oncorhynchus clarkii) and determine if fish utilize the Grand Ditch as a movement corridor. Samples were collected from two sites on the west side and three sites on the east side of the Continental Divide. We identified two or three genetic clusters, and relative migration rates and spatial distributions of admixed individuals indicated that the Grand Ditch facilitated bidirectional fish movement across the Continental Divide, a major biogeographic barrier. Previous studies have demonstrated ecological impacts of interbasin water transfers, but our study is one of the first to use genetics to understand how interbasin water transfers affect connectivity
between previously isolated watersheds. We also discuss implications on native trout management and balancing water demand and biodiversity conservation.
... Cutthroat Trout populations with a well-documented fluvial life history where they ascend tributary streams to spawn but then descend to over winter in the Bear River mainstem (Colyer et al. 2005;Schrank and Rahel 2006;Carlson and Rahel 2010). These systems also have a diverse suite of native non-game fishes that include Northern Leatherside Chub, Mountain Sucker, Mountain Whitefish, and more (Roberts and Rahel 2008). ...
Limited resources for conservation require that conservation be strategic. Spatial conservation prioritization focuses on networks of conservation areas that efficiently maximize the representation of species. The algorithms and software underlying spatial prioritization can now account for the dendritic nature of freshwater systems. As such, spatial prioritization approaches have been applied to native fishes, in part to identify Native Fish Conservation Areas as a framework on which to focus conservation.
The Desert Fish Habitat Partnership (DFHP) is represented by multiple agencies and organizations and focuses on protection and restoration of fish habitats across the western U.S. for 179 native fish species. Likewise, the Western Native Trout Initiative (WNTI) is a multiagency partnership focused on habitat conservation for 21 native trout and char species in 12 western states. These partnerships use multispecies assessments that rank watersheds from 0 (low value for native fishes) to 1 (high value) to help understand whether projects proposed as part of their granting programs fall in important watersheds. The assessments also highlight opportunities for collaboration. However, no such assessments exist for the Bonneville, Lahontan, and Central Nevada basins in the Great Basin.
For this project, multispecies aquatic assessments focused on native fishes were completed for the Bonneville Basin and Lahontan and Central Nevada Basins. The Bonneville Basin assessment was completed for over 29,000 catchments and 19 native fish species, as well as life history diversity (resident, fluvial, adfluvial), genetic diversity, and abundance of Bonneville Cutthroat Trout populations. The Lahontan and Central Nevada Basins assessment covered over 2,000 subwatersheds (HUC12) and 41 native fish species or subspecies, as well as life history diversity, genetic diversity, and abundance of Lahontan Cutthroat Trout populations. Both assessments accounted for aquatic connectivity, and discounted species information in areas of high risk to habitat degradation (e.g., urban areas).
The multispecies assessments highlighted watersheds of high conservation value. In the Bonneville Basin, the Bear River watershed had several areas of high value, such as Bear Lake because of of four species endemic to the lake and adfluvial Bonneville Cutthroat Trout. The Upper Bear River and Smith and Thomas forks of the Bear River ranked high because of the migratory populations of Bonneville Cutthroat Trout and occurrence of native non-game fishes such as Northern Leatherside Chub, Mountain Sucker, Mountain Whitefish, and others. Utah Lake ranked high because it is the only habitat occupied by June Sucker, several wetland complexes ranked high because of the presence of the rare Least Chub, and the Sevier River and its tributaries ranked high because of Bonneville Cutthroat Trout populations and the occurrence of Southern Leatherside Chub and other native species.
In the Lahontan Basin, the Truckee River basin ranked high because of Lahontan Cutthroat Trout in high elevation tributaries, and due to adfluvial Lahontan Cutthroat Trout and Cui-ui in Pyramid Lake at its terminus. The Walker River basin ranked high for similar reasons (but absent of Cui-ui). Willow and Whitehorse creeks in the Coyote Lake basin ranked high because of the genetic distinctness of Lahontan Cutthroat Trout. And many of the endorheic basins in the central Nevada ranked high because of the unique forms of Speckled Dace, Tui Chub, Poolfish, and Springfish that occupy them. Ash Meadows and Devils Hole ranked high as well because of the presence of endemic species found nowhere else.
Some of the high value watersheds identified have both native trout and native non-game species. These Native Fish Conservation Areas represent opportunities for DFHP and WNTI collaboration and have a high return on conservation investment due to their diverse native aquatic communities.
... Some of the routes are advantageous for fish survival and growth, such as those with productive floodplains and side channels [7][8][9]. Others may lead to increased mortality, such as those with agricultural diversions, turbines, industrial cooling systems, or habitats with high predator population [10,11]. A good example is the juvenile Chinook salmon migration from natural tributaries to the ocean in the Sacramento (San Joaquin River Delta, California) a Delta consisting of a complex network of natural and artificial channels and having been highly altered for water conveyance [12]. ...
Flow structures at a river diversion juncture are complex and have been studied extensively. Their impact on the juvenile salmon entrainment into the side channel, however, is less investigated, and based mostly on empiricism. In this study, a Eulerian fish tracking model is developed and used in conjunction with a 3D flow solver to quantitatively evaluate the implications of complex flow characteristics at typical junctures on fish entrainment. First, the flow model is validated with the available experimental data, key flow structures are examined using the results, and their implications for fish entrainment are discussed. Next, the numerical fish tracking model is used to show that the cross-sectional fish distribution immediately upstream of a juncture is an important factor that controls fish entrainment efficiency. Fish entrainment efficiency curves are developed for different flow diversion ratios and fish distribution patterns and used to shed light on the reasons behind some field-observed fish entrainment patterns. Further, the model is used to show that the secondary flow in a river bend may have a significant impact on fish entrainment at flow junctures, in agreement with field observations. Finally, a submerged vane is demonstrated to be a potential management option to locally generate secondary flows upstream of a juncture to achieve the desired fish entrainment property.
... The first is that dispersal into canals is mostly limited to their upstream reaches. Roberts and Rahel (2008) found substantial movement by trout within a large canal system using radio-tracking. ...
... The second potential explanation, however, is declining habitat suitability downstream, particularly in terms of loss of water depth. Roberts and Rahel (2008) found a 77% mortality rate of their radio-tracked fish after flows were diminished at the end of the irrigation season and concluded that dewatering was a major threat to fish survivorship within irrigation systems. We observed large numbers of dead juveniles along the Arno and Shini canals at the end of the irrigation season, and anecdotal reports from nearby farmers were similar (G. ...
Lake Tana is one of East Africa’s largest freshwater bodies, yet many of its fishes are migratory and utilize in-flowing tributaries as critical spawning habitat. However, factors such as expanding water resources developments and sand mining along these rivers and streams may disrupt this ecosystem function. We monitored juvenile and adult fish abundance and water quality across five lake tributaries from August 2014 to April 2015 to examine how irrigation schemes and water quality affect assemblage and population structure. Adult assemblages were dominated by Labeobarbus cyprinids and varied between tributaries, albeit without separation by irrigation development or sand mining. Overall, adult abundances of the dominant migratory Labeobarbus species were four-fold higher below the Shini River irrigation weir than upstream. Contrastingly, juvenile abundances were often significantly higher above these structures. Juvenile abundances decreased on average by 46% along the first 1000 m of two irrigation canals, suggesting poor habitat suitability or high mortalities from water withdrawals. Water quality varied more between rivers than sampling times, but without any separation of tributaries by irrigation or sand mining. Conductivity and turbidity-related parameters had the highest correlation with adult assemblage structure and individual species abundances. These findings indicate that Lake Tana tributaries must be managed on a case by case basis, with more focus given to mechanisms allowing fish to bypass irrigation developments and the direct assessment of fish populations between sand mining and other sites.
... be required depending on the characteristics of canals (see Section 2) and the objectives of management for biodiversity conservation and other purposes. For instance, irrigation canals might suffer from fish entrainment due to the complex canal and ditch networks (Roberts and Rahel, 2008), nutrient loading and sedimentation due to nearby agriculture activities and relatively small channel size (Dollinger et al., 2015), while the main pressures in navigation canals may be physical disturbances such as wake wash by shipping and boating (Zajicek and Wolter, 2019), lack of habitat structures, and poor water quality (Daniels, 2001;Wolter, 2001). For abandoned canals, lack of maintenance over centuries may allow the development of mature successional stages of high conservation value, especially for riparian and aquatic vegetation as well as limnophilic fish and semiaquatic birds, mammals, and invertebrates. ...
While fragmentation and habitat loss due to water infrastructure threaten freshwater biodiversity worldwide, historic canals have the potential to contribute to both cultural heritage and biodiversity conservation. Shifting management objectives regarding historic canals from development to recreation and conservation offer opportunities for achieving conservation targets in these anthropogenic systems. However, managing historic canals often involves multiple objectives (e.g., nature conservation vs historic preservation). We reviewed ecological studies in various types of canal systems, examined the potential of historic canals to contribute to biodiversity conservation, and provided suggestions to promote biodiversity conservation given the opportunities and challenges in canal management. Canal characteristics (e.g., size, main use, surrounding environment, physical and hydrological properties) can be used to qualify or quantify their potential conservation value and risk. Changing management regimes to mimic natural flow, enhance habitat complexity, and modify con-nectivity could improve ecosystem functions and services in canals. To achieve conservation potential of historic canals, studies are required to fill knowledge gaps and to understand trade-offs among often competing objectives. The use of decision analysis such as structured decision making allows managers to incorporate multiple objectives, evaluate trade-offs, and address uncertainties in historic canal management.
... In addition to diverting water, stream diversions can also divert a substantial amount of adult and juvenile fish, resulting in high mortality (Burgi et al. 2006;Roberts and Rahel 2008). This is especially problematic with threatened and endangered fish. ...
Stream restoration practitioners and researchers have devoted a great deal of effort in recent decades to developing extensive guidance for stream restoration. The available resources are diverse, reflecting the wide ranging approaches used and expertise required to develop effective stream restoration projects. To help practitioners in sorting through the extensive amount of available information, this technical note has been developed to provide a guide to the available guidance. The document structure is primarily a series of short literature reviews followed by a hyperlinked reference list for readers to find more information on each topic. The primary topics incorporated into this guidance include general methods, an overview of stream processes and restoration, case studies, data compilation, preliminary assessments, and field data collection. Analysis methods and tools, and planning and design guidance for specific restoration features are also provided. This technical note is a bibliographic repository of information available to assist professionals with the process of planning, analyzing, and designing stream restoration projects. It is updated periodically.
