Design and assessment of weirs for fish passage under drowned conditions

Keller, Robert R.; Peterken, Corinna; Berghuis, Andrew

doi:10.1016/j.ecoleng.2011.06.037

Cited by 12 publications

(8 citation statements)

References 14 publications

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“…However, was significantly influenced by the typology of obstacles, with high and steep obstacles showing an overall effect size 40% higher than low and gentle obstacles (Table 3, Figure 3). This finding is in line with classical expectations about the impact of dam typology (e.g., Januchowski-Hartley et al, 2019) and conclusions from other studies (e.g., Amaral et al, 2019; Keller et al, 2012; Zigler et al, 2004), as well as with the obstacle drowning hypothesis: the highest dams (≥ 2 m) might rarely be drowned (leading to the increase in ), but, in presence of a gentle slope (< 45°), they might become partly crossable by some individuals, at least at intermediate drowning conditions, so that only the highest and steepest obstacles have an overall significant effect size ( = 54.6%; Figure 3). This result should of course be confirmed and refined with additional datasets, but it provides a relevant and meaningful benchmark for practitioners to adjust restoration planning even in the absence of any individual quantification of barrier effects.…”

Section: Discussionsupporting

confidence: 93%

“…These discrepancies illustrate how barrier effects can be highly species- or genus-dependent (Amaral et al, 2021; Blanchet et al, 2010; Prunier et al, 2018), and thus hardly predictable given our limited knowledge about fish movement behavior and capacities (Baudoin et al, 2014; Thurow, 2016). In absence of a dedicated fish pass, individuals are supposed to take advantage of drowned conditions, that is, of periods where water level rises above the height of the dam, to cross the obstacle (Keller et al, 2012). However, such propitious conditions of obstacle drowning might not be encountered every year, at all localities, and equally across all species/individuals, depending on their swimming behavior and capabilities in various environmental conditions and to the timing of submersion compared with the timing of individual movements (Carpenter-Bundhoo et al, 2020; Holthe et al, 2005; Keller et al, 2012).…”

Section: Discussionmentioning

confidence: 99%

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Barrier mitigation measures trigger the rapid recovery of genetic connectivity in five freshwater fish species

Prunier

Loot

Veyssière

et al. 2021

Preprint

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Rivers are heavily fragmented by man-made instream barriers such as dams and weirs. This hyper-fragmentation is a major threat to freshwater biodiversity and restoration policies are now adopted worldwide to mitigate these impacts. However, there is surprisingly little feedback on the efficiency of barrier mitigation measures in restoring riverine connectivity, notably for non-migratory fish species. Here, we implemented a "before-after genetic monitoring" of the restoration of 11 weirs in France using a dedicated genetic index of fragmentation (the FINDEX), with a focus on five fish species from two genera. We found that most obstacles actually had a significant impact on connectivity before restoration, especially the highest and steepest ones, with an overall barrier effect of about 51% of the maximal theoretical impact. Most importantly, we demonstrated for the first time that mitigation measures such as dam removal or fish pass creation significantly and rapidly improved connectivity, with -for some barriers- a complete recovery of the genetic connectivity in less than twelve months. Our study provides a unique and strong proof-of-concept that barrier removal is an efficient strategy to restore riverine connectivity and that molecular tools can provide accurate measures of restoration efficiency within a few months.

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Section: Discussionsupporting

confidence: 93%

Section: Discussionmentioning

confidence: 99%

Barrier mitigation measures trigger the rapid recovery of genetic connectivity in five freshwater fish species

Prunier

Loot

Veyssière

et al. 2021

Preprint

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“…In this context the drown out threshold of a barrier is defined as the river discharge at which the downstream water level rises to a height where it begins to affect flow over a barrier, which is the discharge at which fish have opportunity to move upstream past the barrier (Koehn and Crook, 2013). Many of the drown out values for these barriers are estimates that have not been validated with specific field assessments, but those that have been validated (as per Keller et al, 2012) generally indicate estimates are reasonable at approximating these characteristics (Kerr et al, 2018).…”

Section: Limitations To Fish Movement From In-stream Barriersmentioning

confidence: 99%

Risks to Fish Populations in Dryland Rivers From the Combined Threats of Drought and Instream Barriers

Marshall

Lobegeiger

Starkey³

2021

Front. Environ. Sci.

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In dryland rivers, flow intermittency means fish populations are often subjected to drought disturbance. The viability of these fish populations depends on the availability of waterhole refuges for individuals to survive drought (resistance) and the ability of surviving fish to repopulate the rivers by recruitment and dispersal once flow returns (resilience). In this study we combined remote-sensed mapping of the locations of waterholes that lasted through an extreme drought in the northern Murray Darling Basin, Australia, with an assessment of the impacts of in-stream barriers on limiting the opportunities for fish to move and repopulate after drought. We found that at the peak of this 2018–2020 drought, the worst on record for some rivers and the most spatially synchronous recorded across the region, waterholes were few and generally small – representing only 11% of the total river channel network. All the fish in the region that survived the drought were concentrated into this limited waterhole refuge habitat. Even small instream structures, such as minor weirs, caused large reductions in the opportunities for fish to move between river segments when there is flow. Almost all the 104 instream structures assessed reduced long-term fish movement opportunities, measured as days with discharge greater than calculated barrier drown out thresholds, by more than 70% and up to 100%, when compared to opportunities for movement if the barrier was not present. This large impact from small instream barriers is a consequence of flow intermittency and is likely to reduce fish population resilience and impact the capacity of fish populations to recover after drought. Combining information on the risks posed by limited refuge habitat availability during drought and from reduced movement opportunity following drought allowed us to identify river segments where these combined threats are the greatest risk to viability of local fish populations. Considering the spatial arrangements of these risks provides a means to systematically prioritize mitigation measures such as weir removal to improve fish movement opportunities and local management of key waterholes to increase drought resistance. The approach used here provides a guide for assessing and prioritizing the management of fish population viability risks from drought and fragmentation by barriers in any non-perennial river setting.

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“…Tudorache et al . ; Keller, Peterken & Berghuis ). These approaches are exemplified by the widely used software fishxing (http://www.stream.fs.fed.us/fishxing) and by species‐specific classification trees or connectivity indices developed to classify road crossings according to their passability (Love & Taylor ; Cote et al .…”

Section: Introductionmentioning

confidence: 99%

Assessing the detectability of road crossing effects in streams: mark–recapture sampling designs under complex fish movement behaviours

Pépino

Rodríguez

Magnan

2016

Journal of Applied Ecology

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Centre de recherche sur les interactions bassins versantsecosyst emes aquatiques, Universit e du Qu ebec a Trois-Rivi eres, C.P. 500, Trois-Rivi eres QC G9A 5H7, Canada Summary 1. Most reviews of stream fish connectivity have highlighted the urgent need for standardized methods to quantify the effects of barriers such as road crossings on fish movement and incorporate the complexity of fish behaviours. A question that has not been fully addressed yet in field assessments of fish stream connectivity is which conditions influence the detectability of road crossing effects. Failure to detect existing road crossing effects can result from shortcomings in sampling design that lead to low statistical power. 2. Here, we propose general barrier dispersal models to allow for asymmetry in barrier permeability and changes in movement behaviours of fish confronting a barrier. Despite the increased realism of these ecological assumptions, it remains to be determined whether asymmetric barriers and altered movement behaviours can be unambiguously detected using mark-recapture trials. We used simulations within a modelling framework that explicitly incorporates barrier and behavioural effects to assess the statistical power of various markrecapture sampling designs under different combinations of design and ecological constraints. 3. Key insights from our simulations are that (i) the spatial extent of the study reach critically affects detectability of barrier effects; (ii) the number of recaptured individuals that cross a barrier has greater effect on detectability than the total number of recaptures on both sides of the barrier; and (iii) detectability of asymmetry in barrier permeability and of altered movement behaviours increases with both linear fish density and effect size. 4. Synthesis and applications. The proposed dispersal models, incorporating asymmetric barrier permeability and changes in movement behaviours of fish confronting a barrier, are of broad importance in the quantification of habitat connectivity in streams and rivers. Our simulation approach provides precise guidelines for improving the sampling design by adjusting the spatial extent of the study reach based on a priori knowledge of ecological constraints. This study highlights the importance of evaluating the detectability of the effects of barriers such as road crossings and carefully planning the sampling design of mark-recapture studies before conducting costly field trials and provides quantitative tools to help achieve these goals.

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Design and assessment of weirs for fish passage under drowned conditions

Cited by 12 publications

References 14 publications

Barrier mitigation measures trigger the rapid recovery of genetic connectivity in five freshwater fish species

Barrier mitigation measures trigger the rapid recovery of genetic connectivity in five freshwater fish species

Risks to Fish Populations in Dryland Rivers From the Combined Threats of Drought and Instream Barriers

Assessing the detectability of road crossing effects in streams: mark–recapture sampling designs under complex fish movement behaviours

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