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Rivers of the large Alpine valleys constitute iconic ecosystems that are highly threatened by multiple anthropogenic stressors. This stressor mix, however, makes it difficult to develop and refine conservation and restoration strategies. It is, therefore, urgent to acquire more detailed knowledge on the consequences and interactions of prevalent stressors on fish populations, in particular, on indicator species such as the European grayling Thymallus thymallus. Here, we conducted a multi-river, multi-stressor investigation to analyze the population status of grayling. Using explorative decision-tree approaches, we disentangled the main and interaction effects of four prevalent stressor groups: flow modification (i.e., hydropeaking), channelization, fragmentation, and water quality alteration. Moreover, using a modified variant of the bootstrapping method, pooled bootstrapping, we determined the optimal number of characteristics that adequately describe fish population status. In our dataset, hydropeaking had the strongest single effect on grayling populations. Grayling biomass at hydrological control sites was around eight times higher than at sites affected by hydropeaking. The primary parameters for predicting population status were downramping rate and peak amplitude, with critical ranges of 0.2–0.4 cm min−1 and 10–25 cm. In hydropeaking rivers, river morphology and connectivity were the preceding subordinated parameters. Repeating the procedure with pooled bootstrapping datasets strengthened the hypothesis that the identified parameters are most relevant in predicting grayling population status. Hence, hydropeaking mitigation based on ecological thresholds is key to protect and restore already threatened grayling populations. In hydropeaking rivers, high river network connectivity and heterogenous habitat features can dampen the adverse effects of pulsed-flow releases by offering shelter and habitats for all life cycle stages of fish. The presented approach of explorative tree analysis followed by post-hoc tests of identified effects, as well as the pooled bootstrapping method, offers a simple framework for researchers and managers to analyze multi-factorial datasets and draw solid management conclusions.
Daniel S. Hayes; Erwin Lautsch; Günther Unfer; Franz Greimel; Bernhard Zeiringer; Norbert Höller; Stefan Schmutz. Response of European grayling, Thymallus thymallus, to multiple stressors in hydropeaking rivers. Journal of Environmental Management 2021, 292, 112737 .
AMA StyleDaniel S. Hayes, Erwin Lautsch, Günther Unfer, Franz Greimel, Bernhard Zeiringer, Norbert Höller, Stefan Schmutz. Response of European grayling, Thymallus thymallus, to multiple stressors in hydropeaking rivers. Journal of Environmental Management. 2021; 292 ():112737.
Chicago/Turabian StyleDaniel S. Hayes; Erwin Lautsch; Günther Unfer; Franz Greimel; Bernhard Zeiringer; Norbert Höller; Stefan Schmutz. 2021. "Response of European grayling, Thymallus thymallus, to multiple stressors in hydropeaking rivers." Journal of Environmental Management 292, no. : 112737.
Specific concepts of fluvial ecology are well studied in riverine ecosystems of the temperate zone but poorly investigated in the Afrotropical region. Hence, we examined the longitudinal zonation of fish and adult caddisfly (Trichoptera) assemblages in the endorheic Awash River (1,250 km in length), Ethiopia. We expected that species assemblages are structured along environmental gradients, reflecting the pattern of large-scale freshwater ecoregions. We applied multivariate statistical methods to test for differences in spatial species assemblage structure and identified characteristic taxa of the observed biocoenoses by indicator species analyses. Fish and caddisfly assemblages were clustered into highland and lowland communities, following the freshwater ecoregions, but separated by an ecotone with highest biodiversity. Moreover, the caddisfly results suggest separating the heterogeneous highlands into a forested and a deforested zone. Surprisingly, the Awash drainage is rather species-poor: only 11 fish (1 endemic, 2 introduced) and 28 caddisfly species (8 new records for Ethiopia) were recorded from the mainstem and its major tributaries. Nevertheless, specialized species characterize the highland forests, whereas the lowlands primarily host geographically widely distributed species. This study showed that a combined approach of fish and caddisflies is a suitable method for assessing regional characteristics of fluvial ecosystems in the tropics.
Gernot K. Englmaier; Daniel S. Hayes; Paul Meulenbroek; Yonas Terefe; Aschalew Lakew; Genanaw Tesfaye; Herwig Waidbacher; Hans Malicky; Alemayehu Wubie; Patrick Leitner; Wolfram Graf. Longitudinal river zonation in the tropics: examples of fish and caddisflies from the endorheic Awash River, Ethiopia. Hydrobiologia 2020, 847, 4063 -4090.
AMA StyleGernot K. Englmaier, Daniel S. Hayes, Paul Meulenbroek, Yonas Terefe, Aschalew Lakew, Genanaw Tesfaye, Herwig Waidbacher, Hans Malicky, Alemayehu Wubie, Patrick Leitner, Wolfram Graf. Longitudinal river zonation in the tropics: examples of fish and caddisflies from the endorheic Awash River, Ethiopia. Hydrobiologia. 2020; 847 (19):4063-4090.
Chicago/Turabian StyleGernot K. Englmaier; Daniel S. Hayes; Paul Meulenbroek; Yonas Terefe; Aschalew Lakew; Genanaw Tesfaye; Herwig Waidbacher; Hans Malicky; Alemayehu Wubie; Patrick Leitner; Wolfram Graf. 2020. "Longitudinal river zonation in the tropics: examples of fish and caddisflies from the endorheic Awash River, Ethiopia." Hydrobiologia 847, no. 19: 4063-4090.
Numerous anthropogenic stressors impact rivers worldwide. Hypoxia, resulting from organic waste releases and eutrophication, occurs very commonly in Mediterranean rivers. Nonetheless, little is known about the effects of deoxygenation on the behavior of Mediterranean freshwater fish. To fill this knowledge gap, we assessed the impact of three different dissolved oxygen levels (normoxia, 48.4%, 16.5% saturation) on kinematics indicators (swimming velocity, acceleration, distance traveled) and shoaling cohesion of adult Iberian barbel, Luciobarbus bocagei, a widespread cyprinid species inhabiting a broad range of lotic and lentic habitats. We conducted flume experiments and video-tracked individual swimming movements of shoals of five fish. Our results reveal significant differences between the treatments regarding kinematics. Swimming velocity, acceleration, and total distance traveled decreased stepwise from the control to each of the two oxygen depletion treatments, whereby the difference between the control and both depletion levels was significant, respectively, but not between the depletion levels themselves. Shoaling cohesion showed dissimilarities between the treatments regarding the maximum distance between fish, as the high depletion treatment differed from each of the other two, indicating that under severe oxygen depletion some individuals move away from the shoal. Overall, our results show how oxygen depletion changes fish behavior, which may entail ecological responses, highlighting the need to maintain an unfragmented river network to ensure movement dispersal among habitats, thus providing conditions for species escapement from hypoxia.
Daniel S. Hayes; Paulo Branco; José Maria Santos; Teresa Ferreira. Oxygen Depletion Affects Kinematics and Shoaling Cohesion of Cyprinid Fish. Water 2019, 11, 642 .
AMA StyleDaniel S. Hayes, Paulo Branco, José Maria Santos, Teresa Ferreira. Oxygen Depletion Affects Kinematics and Shoaling Cohesion of Cyprinid Fish. Water. 2019; 11 (4):642.
Chicago/Turabian StyleDaniel S. Hayes; Paulo Branco; José Maria Santos; Teresa Ferreira. 2019. "Oxygen Depletion Affects Kinematics and Shoaling Cohesion of Cyprinid Fish." Water 11, no. 4: 642.
Peak-operating hydropower plants are usually the energy grid’s backbone by providing flexible energy production. At the same time, hydropeaking operations are considered one of the most adverse impacts on rivers, whereby aquatic organisms and their life-history stages can be affected in many ways. Therefore, we propose specific seasonal regulations to protect ecologically sensitive life cycle stages. By reviewing hydropeaking literature, we establish a framework for hydrological mitigation based on life-history stages of salmonid fish and their relationship with key parameters of the hydrograph. During migration and spawning, flows should be kept relatively stable, and a flow cap should be implemented to prevent the dewatering of spawning grounds during intragravel life stages. While eggs may be comparably tolerant to dewatering, post-hatch stages are very vulnerable, which calls for minimizing or eliminating the duration of drawdown situations and providing adequate minimum flows. Especially emerging fry are extremely sensitive to flow fluctuations. As fish then grow in size, they become less vulnerable. Therefore, an ‘emergence window’, where stringent thresholds on ramping rates are enforced, is proposed. Furthermore, time of day, morphology, and temperature changes must be considered as they may interact with hydropeaking. We conclude that the presented mitigation framework can aid the environmental enhancement of hydropeaking rivers while maintaining flexible energy production.
Daniel Hayes; Miguel Moreira; Isabel Boavida; Melanie Haslauer; Günther Unfer; Bernhard Zeiringer; Franz Greimel; Stefan Auer; Teresa Ferreira; Stefan Schmutz. Life Stage-Specific Hydropeaking Flow Rules. Sustainability 2019, 11, 1547 .
AMA StyleDaniel Hayes, Miguel Moreira, Isabel Boavida, Melanie Haslauer, Günther Unfer, Bernhard Zeiringer, Franz Greimel, Stefan Auer, Teresa Ferreira, Stefan Schmutz. Life Stage-Specific Hydropeaking Flow Rules. Sustainability. 2019; 11 (6):1547.
Chicago/Turabian StyleDaniel Hayes; Miguel Moreira; Isabel Boavida; Melanie Haslauer; Günther Unfer; Bernhard Zeiringer; Franz Greimel; Stefan Auer; Teresa Ferreira; Stefan Schmutz. 2019. "Life Stage-Specific Hydropeaking Flow Rules." Sustainability 11, no. 6: 1547.
Hydroelectric power plants managed in response to sub-daily changes of the electricity market undergo rapid variations of turbine discharge, entailing quickly fluctuating water levels downstream. This operation regime, called hydropeaking, causes numerous adverse impacts on river ecosystems. The hydrological alterations which affect hydropeaking rivers can be described by five parameters that change over space and time (magnitude, rate of change, frequency, duration, and timing), where each parameter may be correlated with distinct environmental impacts and therefore may be used to define flow thresholds and set targets for operational mitigation strategies. Thus, this study aims to present an extensive review on the so far established hydropeaking targets and thresholds regarding the outputs from the scientific community as well as from national regulations. We found that only few European countries (Switzerland and Austria) have legal regulations regarding hydropeaking flow thresholds. Other countries, such as Canada and the USA, present environmental legislation that can force hydropeaking mitigation measures. Most mitigation thresholds and management recommendations in literature deal with the effect of downramping on the stranding of salmonids, as well as with minimum flows between peak-flows to avoid spawning ground desiccation. Regarding other fish species and parameters, information on mitigation targets or thresholds is scarcer or non-existent, as well as on hydropeaking mitigation case-studies, resulting in a lack of knowledge and guidelines for its implementation or regulation. Nevertheless, the available literature indicates that multiple aspects must be considered when assessing such values. Thus, to aid in that process, we propose that mitigation targets and thresholds must be based on key species, including particular features regarding season, life-stage and time of day, which must be combined with site-specific morphological characteristics. The presented approach may benefit impacted organism groups in hydropeaking reaches through the establishment of ecologically-based relevant mitigation thresholds and/or targets.
Miguel Moreira; Daniel Hayes; Isabel Boavida; Martin Schletterer; Stefan Schmutz; António Pinheiro. Ecologically-based criteria for hydropeaking mitigation: A review. Science of The Total Environment 2018, 657, 1508 -1522.
AMA StyleMiguel Moreira, Daniel Hayes, Isabel Boavida, Martin Schletterer, Stefan Schmutz, António Pinheiro. Ecologically-based criteria for hydropeaking mitigation: A review. Science of The Total Environment. 2018; 657 ():1508-1522.
Chicago/Turabian StyleMiguel Moreira; Daniel Hayes; Isabel Boavida; Martin Schletterer; Stefan Schmutz; António Pinheiro. 2018. "Ecologically-based criteria for hydropeaking mitigation: A review." Science of The Total Environment 657, no. : 1508-1522.
Periodic assessment of harvested fish populations is essential for their sustainable management. A potential alternative to costly and resource‐intensive electrofishing estimates in clearwater streams is the noninvasive snorkeling method. To assess the utility of snorkeling for the angling community, we compared underwater fish counts carried out by novice snorkelers to state‐of‐the‐art electrofishing depletion estimates. Over two consecutive years, we sampled subadult and adult Brown Trout Salmo trutta and Rainbow Trout Oncorhynchus mykiss with both methods in a fourth‐order mountain stream. In each year, a new team of novice snorkelers collected the data. In total, 12 riffle, pool, and run habitats were sampled, and the homogeneity of abundance and size‐class distribution between the two methods was analyzed. Over both years, we could detect differences in 6 of 24 habitat × species configurations and in 10 of 72 habitat × species × size‐class configurations. Species‐specific behavioral traits and differences in the physical character of the habitats were responsible for a divergence in performance between the two methods. Overall, the observed effects were statistically interpreted as weak, as shown by local tests and the indicated low effect sizes. Snorkeling efficiency, however, remained affected by the effort and abilities of the team, as indicated by the year‐by‐year comparison. We conclude that in clearwater trout streams, snorkeling can be an appropriate substitute method for the widespread, autonomously organized angling community to gather data and build a sound foundation for fisheries‐related decision making, if limitations are considered.
Kurt Pinter; Erwin Lautsch; Günther Unfer; Daniel Hayes. Snorkeling‐Based Fish Stock Assessment by Anglers—A Valuable Method for Managing Recreational Fisheries. North American Journal of Fisheries Management 2018, 39, 82 -90.
AMA StyleKurt Pinter, Erwin Lautsch, Günther Unfer, Daniel Hayes. Snorkeling‐Based Fish Stock Assessment by Anglers—A Valuable Method for Managing Recreational Fisheries. North American Journal of Fisheries Management. 2018; 39 (1):82-90.
Chicago/Turabian StyleKurt Pinter; Erwin Lautsch; Günther Unfer; Daniel Hayes. 2018. "Snorkeling‐Based Fish Stock Assessment by Anglers—A Valuable Method for Managing Recreational Fisheries." North American Journal of Fisheries Management 39, no. 1: 82-90.
Ion, diversion, and storage of flow alter rivers worldwide. In this context, minimum flow regulations are applied to mitigate adverse impacts and to protect affected river reaches from environmental deterioration. Mostly, however, only selected instream criteria are considered, neglecting the floodplain as an indispensable part of the fluvial ecosystem. Based on essential functions and processes of unimpaired temperate floodplain rivers, we identify fundamental principles to which we must adhere to determine truly ecologically-relevant environmental flows. Literature reveals that the natural flow regime and its seasonal components are primary drivers for functions and processes of abiotic and biotic elements such as morphology, water quality, floodplain, groundwater, riparian vegetation, fish, macroinvertebrates, and amphibians, thus preserving the integrity of floodplain river ecosystems. Based on the relationship between key flow regime elements and associated environmental components within as well as adjacent to the river, we formulate a process-oriented functional floodplain flow (ff-flow) approach which offers a holistic conceptual framework for environmental flow assessment in temperate floodplain river systems. The ff-flow approach underlines the importance of emulating the natural flow regime with its seasonal variability, flow magnitude, frequency, event duration, and rise and fall of the hydrograph. We conclude that the ecological principles presented in the ff-flow approach ensure the protection of floodplain rivers impacted by flow regulation by establishing ecologically relevant environmental flows and guiding flow restoration measures.
Daniel S. Hayes; Julia M. Brändle; Carina Seliger; Bernhard Zeiringer; Teresa Ferreira; Stefan Schmutz. Advancing towards functional environmental flows for temperate floodplain rivers. Science of The Total Environment 2018, 633, 1089 -1104.
AMA StyleDaniel S. Hayes, Julia M. Brändle, Carina Seliger, Bernhard Zeiringer, Teresa Ferreira, Stefan Schmutz. Advancing towards functional environmental flows for temperate floodplain rivers. Science of The Total Environment. 2018; 633 ():1089-1104.
Chicago/Turabian StyleDaniel S. Hayes; Julia M. Brändle; Carina Seliger; Bernhard Zeiringer; Teresa Ferreira; Stefan Schmutz. 2018. "Advancing towards functional environmental flows for temperate floodplain rivers." Science of The Total Environment 633, no. : 1089-1104.