Luiz G. M. Silva

Last Name

M. Silva

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Luiz G.

ORCID

0000-0002-2329-5601

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09467 - Stocker, Roman / Stocker, Roman

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Publications 1 - 10 of 15

Towards vibrant fish populations and sustainable fisheries that benefit all: learning from the last 30 years to inform the next 30 years
Cooke, Steven J.; Fulton, Elizabeth A.; Sauer, Warwick H.H.; et al. (2023)
Reviews in Fish Biology and Fisheries
A common goal among fisheries science professionals, stakeholders, and rights holders is to ensure the persistence and resilience of vibrant fish populations and sustainable, equitable fisheries in diverse aquatic ecosystems, from small headwater streams to offshore pelagic waters. Achieving this goal requires a complex intersection of science and management, and a recognition of the interconnections among people, place, and fish that govern these tightly coupled socioecological and sociotechnical systems. The World Fisheries Congress (WFC) convenes every four years and provides a unique global forum to debate and discuss threats, issues, and opportunities facing fish populations and fisheries. The 2021 WFC meeting, hosted remotely in Adelaide, Australia, marked the 30th year since the first meeting was held in Athens, Greece, and provided an opportunity to reflect on progress made in the past 30 years and provide guidance for the future. We assembled a diverse team of individuals involved with the Adelaide WFC and reflected on the major challenges that faced fish and fisheries over the past 30 years, discussed progress toward overcoming those challenges, and then used themes that emerged during the Congress to identify issues and opportunities to improve sustainability in the world's fisheries for the next 30 years. Key future needs and opportunities identified include: rethinking fisheries management systems and modelling approaches, modernizing and integrating assessment and information systems, being responsive and flexible in addressing persistent and emerging threats to fish and fisheries, mainstreaming the human dimension of fisheries, rethinking governance, policy and compliance, and achieving equity and inclusion in fisheries. We also identified a number of cross-cutting themes including better understanding the role of fish as nutrition in a hungry world, adapting to climate change, embracing transdisciplinarity, respecting Indigenous knowledge systems, thinking ahead with foresight science, and working together across scales. By reflecting on the past and thinking about the future, we aim to provide guidance for achieving our mutual goal of sustaining vibrant fish populations and sustainable fisheries that benefit all. We hope that this prospective thinking can serve as a guide to (i) assess progress towards achieving this lofty goal and (ii) refine our path with input from new and emerging voices and approaches in fisheries science, management, and stewardship.
Fine-scale movement response of juvenile brown trout to hydropeaking
Naudascher, Robert; Boes, Robert; Fernandez, Vicente; et al. (2024)
Science of The Total Environment
Juvenile fish are known to be the most impacted during hydropeaking events due to stranding or uncontrolled drift resulting from changes to water depth and flow velocity. To shed light on their response to such hydraulic alterations, we coupled flume experiments with image-based fish tracking and quantified the fine-scale movement behavior of wild (n = 30) and hatchery-reared (n = 38) brown trout (Salmo trutta) parr. We exposed fish to two distinct hydropeaking treatments in a laterally inclined (14 %) flume section stocked with real cobbles to create refuge and heterogeneous hydraulic conditions. Fish were individually acclimated (20 min) to baseflow (Q = 1.6 L s-1) and then exposed to three consecutive hydropeaking events, reaching peakflows tenfold larger than baseflow (Q = 16 L s-1). We found that, within just minutes, fish exhibited fine-scale movement responses to cope with the change of hydrodynamic conditions. Fish moved perpendicular to the main flow direction to shallow areas as these became submerged during discharge increase, holding position at low velocity zones. This resulted in a significant difference (p < 0.001) in lateral occupancy of the experimental section between baseflow and peakflow. During peakflow, fish occupied specific positions around cobbles and exhibited swimming behaviors, including bow-riding and entraining, that allowed them to hold position while likely minimizing energy expenditure. As a result, swimming distance reduced 60–70 % compared to baseflow. During the decrease in discharge following peakflow, fish abandoned areas falling dry by moving laterally. In the treatment with the larger down-ramping rate, the time to initiate relocation was lower while the relocation speed was higher. This study shows that, for the conditions investigated here, brown trout parr is capable of swiftly deploying multiple behavioral responses to navigate rapid changes in hydrodynamic conditions. These findings can be incorporated into habitat modeling and improve our capacity to inform hydropeaking mitigation efforts.
Quantifying hydraulic conditions and passage efficiency for an upstream fish passage: a case study from Schiffmühle
Wyss, Andris; Dubach, Tina; Albayrak, Ismail; et al. (2024)
Proceedings of the 10th International Symposium on Hydraulic Structures (ISHS 2024)
River fragmentation by hydropower plants (HPP) can block or delay fish migration. Fish passages have been used to restore river connectivity and maintain fish movements. The design of upstream fish passages has been consolidated in the literature, resulting in the existence of many well-established guidelines. However, the efficiency of fish passages has to be assessed by monitoring programmes that, ideally, include quantification of hydraulic features and fish movements. In this study, the hydraulic and biological performance of a fish passage at the HPP Schiffmühle, Switzerland, was assessed. The HPP Schiffmühle is located in the Limmat River. The fish passage combines nature-like and vertical slot passages with two entrances. Fish movements within the fish passage were quantified using Passive Integrated Transponder (PIT) tags. Hydraulic measurements focused on quantifying the flow fields in the tailrace, around the fish passage entrances, and within selected pools to assess the attraction flow and the hydraulic conditions within the fish passage. The results showed that fish passage efficiency varied between 62% to 81% for different fish species and most fish species passed within a relatively short time of 1-2 hours in the median. However, passage times of about 15 hours (median) were also recorded for some species. This longer passage time is partly explained by frequent individual movements within pools of the fish passage.
Resilience of terrestrial and aquatic fauna to historical and future wildfire regimes in western North America
Jager, Henriette I.; Long, Jonathan W.; Malison, Rachel L.; et al. (2021)
Ecology and Evolution
Wildfires in many western North American forests are becoming more frequent, larger, and severe, with changed seasonal patterns. In response, coniferous forest ecosystems will transition toward dominance by fire-adapted hardwoods, shrubs, meadows, and grasslands, which may benefit some faunal communities, but not others. We describe factors that limit and promote faunal resilience to shifting wildfire regimes for terrestrial and aquatic ecosystems. We highlight the potential value of interspersed nonforest patches to terrestrial wildlife. Similarly, we review watershed thresholds and factors that control the resilience of aquatic ecosystems to wildfire, mediated by thermal changes and chemical, debris, and sediment loadings. We present a 2-dimensional life history framework to describe temporal and spatial life history traits that species use to resist wildfire effects or to recover after wildfire disturbance at a metapopulation scale. The role of fire refuge is explored for metapopulations of species. In aquatic systems, recovery of assemblages postfire may be faster for smaller fires where unburned tributary basins or instream structures provide refuge from debris and sediment flows. We envision that more-frequent, lower-severity fires will favor opportunistic species and that less-frequent high-severity fires will favor better competitors. Along the spatial dimension, we hypothesize that fire regimes that are predictable and generate burned patches in close proximity to refuge will favor species that move to refuges and later recolonize, whereas fire regimes that tend to generate less-severely burned patches may favor species that shelter in place. Looking beyond the trees to forest fauna, we consider mitigation options to enhance resilience and buy time for species facing a no-analog future.
Mortality events resulting from Australia's catastrophic fires threaten aquatic biota
M. Silva, Luiz G.; Doyle, Katherine E.; Duffy, Deanna; et al. (2020)
Global Change Biology
Passage stromabwärts schwimmender Fische an einem Bypass-Einlauf mit bodennaher Öffnung
Kastinger, Maximilian; Albayrak, Ismail; M. Silva, Luiz G.; et al. (2023)
Wasserbau - krisenfest und zukunftsweisend. Beiträge zum 21. Wasserbau-Symposium der Wasserbauinstitute TU München. Tagungsband 2
Infolge gesetzlicher Grundlagen (EU-Wasserrahmenrichtlinie, Schweizer Gewässerschutzgesetz) haben der Fischschutz und Fischabstieg an Wasserkraftanlagen (WKA) in den letzten Jahren in Mitteleuropa stark an Bedeutung gewonnen. In der Schweiz müssen bis 2030 an rund 700 WKA Fischabstiegsanlagen saniert oder neu errichtet werden (Baumgartner et al., 2020). Fischleitrechen (FLR) mit anschließendem Bypass-System (BS) sind für viele Fischarten ein wirkungsvolles System für die sichere Passage stromabwärts. Für eine hohe Akzeptanz des BS ist unter anderem ein ausreichender Bypass-Durchfluss erforderlich, welcher jedoch bei WKA in der Regel für die Stromproduktion verloren geht. Daher wird zur Regulierung des Bypass-Durchflusses häufig eine vertikalachsige Klappe mit lokalen Öffnungen beim Bypass-Einlauf installiert. Durch die räumliche Konzentration des Durchflusses kommt es jedoch in diesen Öffnungen zu hohen Fließgeschwindigkeiten und Geschwindigkeitsgradienten, die zu Vermeidungsreaktionen bei sich nähernden Fischen führen können. Um die Akzeptanz einer bodennahen Bypass-Einlauföffnungen zu untersuchen, wurden ethohydraulische Laborversuche mit Bachforellen (Salmo trutta) und Barben (Barbus barbus) durchgeführt. Messungen der Geschwindigkeitsfelder bestätigten die starke Beschleunigung der Strömung unmittelbar vor und in der Einlauföffnung, welche bei beiden Fischarten häufig zu einem Vermeidungsverhalten führte. Barben zeigten dabei im Vergleich zu Bachforellen eine größere Sensibilität gegenüber hoher Geschwindigkeitsgradienten. Die maximale Bypass-Passage-Effizienz betrug für Bachforellen 59 % und für Barben 52 %. Diese wurde für Bachforellen bei einer Anströmgeschwindigkeit von Uo = 0.4 m/s erreicht, während Barben für Uo = 0.3 m/s die höchste Bypass-Akzeptanz aufwiesen. Die Versuchsergebnisse verdeutlichen, dass Bypass-Einlaufklappen zur Regulierung des Durchflusses die Bypass-Akzeptanz und somit die Fischleiteffizienz des gesamten FLR-BS beeinträchtigen können. Um die Gestaltung des Bypass-Einlaufs zu optimieren und dessen Akzeptanz zu verbessern, sind weitere ethohydraulische Untersuchungen erforderlich.
Boyle’s Law ignores dynamic processes in governing barotrauma in fish
Kerr, James R.; White, Paul Robert; Leighton, Timothy G.; et al. (2023)
Scientific Reports
The expansion and potential rupture of the swim bladder due to rapid decompression, a major cause of barotrauma injury in fish that pass through turbines and pumps, is generally assumed to be governed by Boyle’s Law. In this study, two swim bladder expansion models are presented and tested in silico. One based on the quasi-static Boyle’s Law, and a Modified Rayleigh Plesset Model (MRPM), which includes both inertial and pressure functions and was parametrised to be representative of a fish swim bladder. The two models were tested using a range of: (1) simulated and (2) empirically derived pressure profiles. Our results highlight a range of conditions where the Boyle’s Law model (BLM) is inappropriate for predicting swim bladder size in response to pressure change and that these conditions occur in situ, indicating that this is an applied and not just theoretical issue. Specifically, these conditions include any one, or any combination, of the following factors: (1) when rate of pressure change is anything but very slow compared to the resonant frequency of the swim bladder; (2) when the nadir pressure is near or at absolute zero; and (3) when a fish experiences liquid tensions (i.e. negative absolute pressures). Under each of these conditions, the MRPM is more appropriate tool for predicting swim bladder size in response to pressure change and hence it is a better model for quantifying barotrauma in fish.
Gambusia holbrooki Survive Shear Stress, Pressurization and Avoid Blade Strike in a Simulated Pumped Hydroelectric Scheme
Doyle, Katherine E.; Ning, Nathan; M. Silva, Luiz G.; et al. (2020)
Frontiers in Environmental Science
Pumped hydroelectric energy storage (PHES) projects are being considered worldwide to achieve renewable energy targets and to stabilize baseload energy supply from intermittent renewable energy sources. Unlike conventional hydroelectric systems that only pass water downstream, a feature of PHES schemes is that they rely on bi-directional water flow. In some cases, this flow can be across different waterbodies or catchments, posing a risk of inadvertently expanding the range of aquatic biota such as fish. The risk of this happening depends on the likelihood of survival of individuals, which remains poorly understood for turbines that are pumping rather than generating. This study quantified the survival of a globally widespread and invasive poeciliid fish, Eastern gambusia (Gambusia holbrooki), when exposed to three hydraulic stresses characteristic of those experienced through a PHES during the pumping phase. A shear flume and hyperbaric chamber were used to expose fish to different strain rates and rapid and sustained pressurization, respectively. Blade strike models were also used to predict fish survival through a Francis dual turbine/pump. Simulated ranges were based on design and operational conditions provided for a PHES scheme proposed in south-eastern Australia. All gambusia tested survived high levels of shear stress (up to 1,853 s−1), extremely high pressurization (up to 7,600 kPa gauge pressure) and the majority (>93%) were unlikely to be struck by a turbine blade. Given their tolerance to these extreme simulated stresses, we conclude that gambusia will likely survive passage through the simulated PHES scheme if they are entrained at the intake. Therefore, where a new PHES project poses the risk of inadvertently expanding the range of gambusia or similar poeciliid species, measures to minimize their spread or mitigate their ecosystem impacts should be considered.
Hydropower and Fish: A Roadmap for Best Practice Management
Albayrak, Ismail; Baumgartner, Lee; Boes, Robert; et al. (2022)
The development of a hydropower facility has, in nearly all cases, some impact on natural river flows and the wider environment. This impact often includes the effect on fish, most notably curtailment of migration routes and changes to their natural habitat and ecosystem services fish is dependent on.
The general relationship between fish and hydropower development and management has been the subject of extensive research for many years. However, most of the previous work has been based on a limited number of species, with the applicability of results on a global scale difficult to justify. With the further development of hydropower planned on a global scale, a program of international collaborative research is justified.
This document identifies emerging best practices for managing hydropower and fish, by addressing relevant measures to mitigate changes in hydro-morphological conditions, water quality and quantity due to hydropower development. Where relevant, some of the most mature solutions are described as providing safe two-way connectivity for fish past barriers created by hydropower infrastructures. As such, it serves as a valuable resource for practitioners in the hydropower sector by providing a clear pathway toward viable solutions to the identified challenges for fish and hydropower.
Future-proofing the emergency recovery plan for freshwater biodiversity
Lynch, Abigail J.; Hyman, Amanda A.; Cooke, Steven J.; et al. (2024)
Environmental Reviews
Freshwater biodiversity loss is accelerating globally, but humanity can change this trajector y through actions that enable recovery. To be successful, these actions require coordination and planning at a global scale. The Emergenc y Recove r y Plan for global freshwater biodiversity aims to reduce the risk for freshwater biodiversity loss through six priority actions: (1) acceler-ate implementation of environmental flows; (2) improve water quality to sustain aquatic life; (3) protect and restore critical habitats; (4) manage exploitation of freshwater species and riverine aggregates; (5) prevent and control nonnative species in-vasions in freshwater habitats; and (6) safeguard and restore freshwater connectivity. These actions can be implemented using future-proofing approaches that anticipate future risks (e.g., emerging pollutants, new invaders, and synergistic effects) and minimize likely stressors to make conservation of freshwater biodiversity more resilient to climate change and other global environmental challenges. While uncertainty with respect to past observations is not a new concer n for freshwater biodiver-sity, future-proofing has the distinction of accounting for the uncertainty of futu r e conditions that have no historical baseline. The level of uncertainty with respect to future conditions is unprecedented. Future-proofing of the Emergenc y Recover y Plan for freshwater biodiversity will require anticipating futu r e changes and developing and implementing actions to address those futu r e changes. Here, we showcase future-proofing approaches likely to be successful using local case studies and examples. Ensuring that response options with i n the Emergenc y Recover y Plan ar e future-proofed wi l l provide decision makers with science-informed choices, even in the face of uncertain and potentially new future conditions. We are at an inflection point for global freshwater biodiversity loss; learning from defeats and successes can support improved actions toward a sustainable future.

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Luiz G. M. Silva

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