Ethohydraulics: A Method for Nature-Compatible Hydraulic Engineering 3658354151, 9783658354152

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Boris Lehmann · Katharina Bensing Beate Adam · Ulrich Schwevers Jeffrey A. Tuhtan

Ethohydraulics A Method for Nature-Compatible Hydraulic Engineering

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Boris Lehmann · Katharina Bensing · Beate Adam · Ulrich Schwevers · Jeffrey A. Tuhtan

Ethohydraulics A Method for Nature-Compatible Hydraulic Engineering

Boris Lehmann Fachgebiet für Wasserbau und Hydraulik Technische Universität Darmstadt Darmstadt, Germany

Katharina Bensing Fachgebiet für Wasserbau und Hydraulik Technische Universität Darmstadt Darmstadt, Germany

Beate Adam Institut für angewandte Ökologie GmbH Kirtorf, Germany

Ulrich Schwevers Institut für angewandte Ökologie GmbH Kirtorf, Germany

Jeffrey A. Tuhtan Centre for Biorobotics Tallinn University of Technology Tallinn, Estonia

ISSN 2197-6708 ISSN 2197-6716 (electronic) essentials ISSN 2731-3107 ISSN 2731-3115 (electronic) Springer essentials ISBN 978-3-658-35415-2 ISBN 978-3-658-35416-9 (eBook) https://doi.org/10.1007/978-3-658-35416-9 © Springer Fachmedien Wiesbaden GmbH, part of Springer Nature 2022 The translation was done with the help of artificial intelligence (machine translation by the service DeepL.com). A subsequent human revision was done primarily in terms of content. This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Responsible Editor: Simon Rohlfs This Springer imprint is published by the registered company Springer Fachmedien Wiesbaden GmbH part of Springer Nature. The registered company address is: Abraham-Lincoln-Str. 46, 65189 Wiesbaden, Germany

What You Can Find in This essential

• Structural measures on and in watercourses impair the habitat for the local fauna and flora. • Ethohydraulics allows the hydraulic-reactive behaviour of aquatic animals (especially fish) to be • aquatic animals (especially fish) with laboratory and field studies for various hydraulic • hydraulic situations (influenced by measures). • From the behavioural findings obtained in this way, engineering design, dimensioning and • The behavioural findings obtained in this way can be used to derive engineering design, dimensioning and planning recommendations for fauna-compatible hydraulic engineering facilities. The focus of ethohydraulic investigations is on the design of fish-passable structures (e.g. fish ladders or fish ladders). • fish ladders or fish ladders) or protective structures (e.g. rakes with fish guidance function). • rakes with fish guidance function). • Ethohydraulic investigations are based on three main phases (preliminary analysis, • ethohydraulic test, transfer), which are methodically linked to each other • (situational similarity, ethohydraulic signature). • Besides examples of ethohydraulic investigations and findings, new developments and • new developments and extensions of possible investigation methods are presented.

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Preface

With the statement “If you want to study fish, it is best to become a fish yourself”, the world-famous marine scientist Jacques-Yves Cousteau (1910-1997) expressed something that can certainly be named as an idea for the discipline of ethohydraulics. The environmental policy goals set in the European Union for good ecological quality of surface waters (European Parliament and Council of the European Union [EU], 2000) require that anthropogenic impacts on our flowing waters be as compatible as possible for aquatic fauna. Hydraulic engineering measures such as renaturation and the construction of facilities to create longitudinal passability at transverse structures thus represent a current challenge for engineers and aquatic ecologists alike. Cousteau’s idea had already been published in 1912 by hydraulic engineer Paul Gerhardt with a special focus on his discipline: “If you want to properly design and construct structures that are intended to serve fishing purposes, you have to be familiar with the habits of fish” (Gerhardt, 1912). The habits of fish can be easily determined using the methods of comparative behavioural research - ethology: how do fish perceive their environment? How do they orient themselves in the river? What services can fish perform? Hydraulic engineering experiments can provide the necessary hydraulic environment in a conditioned form. Therefore, the transdiscipline ethohydraulics was conceived by biologists and hydraulic engineers from the methodological union of both disciplines - ethology and hydraulics (Adam and Lehmann, 2011). Since then, ethohydraulics has been successfully applied to many relevant issues and is constantly being further developed. Currently, ethohydraulic investigations represent an important method for the development of general recommendations, limit and guideline values for fishpassable facilities. Furthermore, they serve as an investigation method for the planning and optimisation of complex facilities and their compatibility with

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nature. This essentials is dedicated to this idea of a transdiscipline, describes the background and the essential methodological steps, shows some findings but also pitfalls and gives an outlook on the future of this discipline. In addition, a number of examples are embedded, which provide vivid insights. We hope you enjoy reading this book. Boris Lehmann Katharina Bensing Beate Adam Ulrich Schwevers Jeffrey A. Tuhtan

Literature Adam, B., & Lehmann, B. (2011). Ethohydraulik – Grundlagen, Methoden, Erkenntnisse. Springer. Europäisches Parlament und Rat der Europäischen Union. (2000). Richtlinie 2000/60/EG des Europäischen Parlaments und Rates der Europäischen Union vom 23. 10. 200 zur Schaffung eines Ordnungsrahmens für Maßnahmen der Gemeinschaft im Bereich der Wasserpolitik. Amtsblatt der Europäischen Gemeinschaften L 327/1-327/72 vom 22.12.2000. Gerhardt, P. (1912). Die Fischwege. In Handbuch der Ingenieurwissenschaften, 3. Teil, II. Bd., 1. Abt. Wehre und Fischwege (S. 454–499).

Contents

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 The Problem: “… A Fish’s Nature is to Wander!” . . . . . . . . . . . . . 1.2 First Aid for Migratory Fish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 Transdiscipline Ethohydraulics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Literature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1 1 3 6 8

2 Philosophy and Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 Phase 1: Preliminary Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Situational Similarity as a Transition . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Phase 2: Ethohydraulic Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4 The Ethohydraulic Signature as a Transition . . . . . . . . . . . . . . . . . . . 2.5 Phase 3: Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Literature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11 12 15 16 18 21 21

3 Examples from Practice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 The Pitfalls of Ethohydraulics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Ethohydraulic Findings for Hydraulic Engineering Practice . . . . . . Literature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

23 23 30 40

4 Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 Possibilities and Limits of Statistical Evaluation . . . . . . . . . . . . . . . 4.2 Possibilities of Measurement and Observation Techniques . . . . . . . 4.3 Future Prospects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Literature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

43 44 44 55 55

Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Introduction Ethology and Hydraulics—How are They Related?

Introduction Humans exert a powerful influence on a wide range of environmental processes and cumulatively, our activities have decisive impacts on nearly all of Earth’s ecosystems—it is the age of the Anthropocene. Across the spectrum of natural to cultural landscapes, flowing waters have been heavily modified to satisfy the needs of every ancient and modern society; for energy generation, flood regulation, irrigation and to improve their navigability. In satisfying these needs, we have segmented our flowing waters with numerous barriers. Although many of these structures are passable for ships and boats by means of locks and lifts, they act as “dead ends” for many aquatic organisms, some of which are even forced to take the dangerous and often fatal path through a hydropower turbine in their pursuit of downstream migration. But why?

1.1

The Problem: “… A Fish’s Nature is to Wander!”

The continuity of flowing waters is essential for many fish species to ensure their survival. For example, anadromous and catadromous fish species need to migrate between the sea and inland waters during their life cycle for growth and to lay their eggs (Fig. 1.1). Due to their broad historical relevance, salmon and eel species are the most frequently mentioned ana- and catadromous migratory fish, but the migratory activity of potamodromous fish species is also essential. Many species can travel vast distances within the inland system, and the segmentation of rivers by nonpassable instream barriers can decimate entire populations (Schwevers & Adam, 2020). The reasons for fish migrations can be multifaceted, for example to ideally © Springer Fachmedien Wiesbaden GmbH, part of Springer Nature 2022 B. Lehmann et al., Ethohydraulics, Springer essentials https://doi.org/10.1007/978-3-658-35416-9_1

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Ethology and Hydraulics—How are They Related?

Fig. 1.1 The general classification of migratory fish shows the importance of longitudinal continuity of inland waters: oceanodromous species migrate within the sea and potamodromous within inland waters; diadromous species migrate between saltwater and freshwater and are further divided into anadromous, amphidromous and catadromous species

exploit resources in terms of food, growth, reproduction or to protect themselves from predators. Lucas and Baras (2001) distinguish between different types of migrations as: • seasonal migrations (spawning migration, spawning return migration, larval dispersal by drift, migrations to feeding and winter habitats), • migrations due to catastrophes (drift, compensatory migrations after floods, protective migrations during floods or other unfavourable environmental conditions), • daily roaming (temperature-related, food-related) and, • migrations of unknown cause (upstream migration of mainly juvenile fish in autumn). Regardless of the reasons for migrating, the habitat of aquatic fauna is not solely restricted by instream barriers which are transverse to the direction of flow. Structural diversity has also been strongly altered in the longitudinal direction, thus impairing the habitats of many species. For example, river straightening and

1.2 First Aid for Migratory Fish

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embankments have led to massive losses of floodplains and an impoverishment of submerged structures. These changes highlight the rapid losses to the ecologically sensitive habitats of flowing waters within a relatively short period of time. It is now imperative to take effective measures to preserve the habitat of flowing waters, and reestablish and sustain its connectivity with the surrounding ecosystems. Precisely for this reason, the preservation of river continuity to sustain biodiversity is a core requirement of modern environmental policy, as established in the European Water Framework Directive (EU 2000), the German Federal Water Act and many other international and national laws, decrees and directives.

1.2

First Aid for Migratory Fish

Ecologically, the best solution for the fauna of flowing waters is to remove all barriers to free migration, giving both the watercourse and its inhabitants the space they need to develop, and to restore continuous habitats with high structural and flow diversity needed to sustain aquatic fauna. However, this is often not undertaken due to continuing human uses and the economic and social interests behind them. For this reason, attempts are being made to restore the connectivity of watercourses by means of artificial migration facilities guiding flow around barriers, or by partially removing them. Depending on the direction of fish migration, a distinction is made between fishways and fish protection and descent facilities. For this purpose, simplified planning and dimensioning approaches have been developed, and are provided in several international studies in laboratories and at pilot plants, and which are also included in regulations and guidelines (Silva et al., 2018; Deutsche Vereinigung für Wasserwirtschaft, Abwasser und Abfall e. V. [DWA], 2005, 2014; Ministry for the Environment and Conservation, Agriculture and Consumer Protection of the State of North Rhine-Westphalia [MUNLV], 2005; Gough et al., 2012; Larinier et al., 2002; Bates, 2000). Although there are a wide variety of recommendations and planning approaches, their site-specific suitability and integration into the local environment must always be taken into account first and foremost. Fishways are built to be used by migratory aquatic animals as they swim against the current and usually consist of individual basins lined up sequentially, which gradually reduce the difference in water level height between the headwater and tailwater at a transverse structure. This can be done in multiple ways. If space is available, near-natural bypass channels similar to a stream can be built. Fish protection and descent facilities are passed in the direction of flow by

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mitratory aquatic animals, and fish protection often consists of a screen (e.g. a protective rack) to prevent the animals from swimming into dangerous areas (e.g. a hydropower turbine) guiding them into a bypass which terminates safely in the tailwater. The fish protection screen should be designed in such a way that the actively migrating animals are guided towards the bypass as quickly as possible (Fig. 1.2). Despite current regulations and recommendations for the construction of fishways and descent and protection facilities, there remains large knowledge gaps about the behaviour of fish, especially in response to the many different types of flow they experience in nature. This fundamental problem of linking fish behaviour to flow characteristics during passage is not a new issue. As early as 1874, the Fisheries Act for the Prussian State (“Fischereigesetz für den Preußischen Staat”) required that passage for migratory fish should be made possible at migration barriers (see §35 “Fish passes”). Since then, numerous fishways have been built. Unfortunately, despite good intentions, detailed monitoring of these facilities has conclusively shown that the majority of them are only partially functional, and many are not functional at all (Adam, 2010). This has caused many in academia and industry to wonder, what are the underlying reasons for this? After decades of research, we now know that there are two critical aspects in ensuring that fish migration is successful: the ability for fish to find them, and the ability of fish to pass through them. The fishway must be built and maintained so that the migratory animal can find it without too much effort or delay when approaching the barrier. This sounds simple, but in practice it can be an enormous challenge, especially in the case of wide rivers with many different barriers and complex flows. Once the entry into the fishway has been found, a species-specific migration corridor must be available within the structure itself so that the fish willing to migrate can pass through it without stress and major loss of energy or time. In view of the biomechanical processes for locomotion and the orientation of many aquatic animals to the flow, the migration corridor is defined by the local geometric (e.g. the width of the fishway entrance) and hydraulic (e.g. flow velocity) conditions. This leads to the following questions: what demands do aquatic animals naturally have on the geometric and hydraulic conditions in their habitat? How can water currents be used as “hydraulic signposts” to guide animals willing to migrate through complex and often unnatural situations? The detailed scientific observation of fish behaviour in flowing water bodies is usually limited to scale laboratory flume studies due to the vast range of natural conditions which often include poor visibility in turbid waters and the need for vegetative or rocky cover for many species. In addition, field conditions

1.2 First Aid for Migratory Fish

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Fig. 1.2 Schematic overview of current types of fishways, fish screens and bypass channels

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cannot be conditioned and observations are difficult to interpreted under varying environmental and flow conditions. To begin to answer these difficult questions, specific types of experimental setups, physical settings and observational procedures must be developed using a standardized methodology. The main objective is to observe and uncovering a fish’s characteristic response to a controlled and realisitc flow stimulus. It is therefore undeniable that laboratory conditions are the most suitable for this purpose. But how can complex hydraulic engineering situations with living fish realistically lead to practical findings in a laboratory at a reasonable cost?

1.3

Transdiscipline Ethohydraulics

Aquatic organisms move more like astronauts then earthlings, and make use of the entire water column and the full three-dimensionally of space. In addition, the turbulent currents that surround them can either increase or reduce swimming efficiency. Turbulence in flowing waters also carries information in the form of tiny pressure and water speed fluctuations, allowing fish to automatically orient themselves to their environment. Over millions of years of evolution, fish have developed a unique sensory organ with which they can even detect predators, prey and underwater objects using “touch at a distance” via their lateral line organ (Bleckmann et al., 2004). This stimulus perception often drives fish behaviour as a response to flow stimuli in many situations of practical importance. For example, if a stimulus threshold is exceeded, the information is passed on to the central nervous system of the fish and processed there, which in turn results in a coordinated movement (Fig. 1.3). Ethohydraulic studies then record this movement, which can be interpreted as a reaction to the flow stimulus (Costa et al., 2019). Example: Rheotactic Orientation of Fish in a Uniform Flow

A classic example of how fish react to flows is based on the observation that for many fish species, fish align themselves according to the direction of the flow only after a certain threshold velocity is present. This commonly observed behaviour is called rheotaxis: positive rheotaxis is when the fish aligns itself head first against the current, and negative rheotaxis is when it aligns itself head first in the direction of the current. The difficulty in investigating the speed at which a rheotactic orientation of fish occurs lies in “separating” the stimulus threshold. Through their various

1.3 Transdiscipline Ethohydraulics

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Fig. 1.3 The sensory organs of a fish and possible environmental stimuli (top) and the path from environmental stimulus to response (bottom)

sensory organs, fish also detect a variety of other environmental influences (e.g. optical and acoustic stimuli in the body of water as well as haptic stimuli when touching contours and surfaces). These stimuli overlap and sum, leading to a situation-specific behaviour, which can be of a different nature than just the flow stimulus itself. In addition, the stimulus thresholds of fish, and thus also their perception, differ not only between the different fish species but also within species, for example, depending on their life stage. Ethohydraulics researchers are constantly on the search for new and meaningful stimulus-response combinations. The stimulus must be filtered out from the mass of environmental influences, and carefully evaluated under controlled laboratory conditions. Other stimuli cannot be completely removed, even in laboratory experiments. However, they can be kept constant or selectively intensified in the context of validation experiments. The primary stimulus set in the experiment should then be characterized as a reproducible behaviour, and its transferability

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Fig. 1.4 The transdiscipline ethohydraulics results from the intersection of the disciplines ethology and hydraulics: behavioural observations upstream of a bypass to investigate fish descent (top left); flow signature in the experiment (bottom left); graphical overlay of stimulus and behaviour (right)

to the natural situation should be meaningfully demonstrated. It is precisely for this purpose that the transdiscipline of ethohydraulics was created, to ensure that laboratory studies provide useful results for the field conditions experienced by wild fish (Fig. 1.4). In the next chapter, we discuss the methods used in ethohydraulic laboratory tests in order to ensure that the results are as repeatable and transferrable as possible.

Literature Adam, B. (2010). Anforderungen an die lineare und laterale Durchgängigkeit. Fischwanderung und die Bedeutung der Auenhabitate. BfN-Skripten, 280, 12–25. Bates, K. (2000). Fishway guidelines for Washington State (Richtlinien-Entwurf 4/25/00). Washington Department of Fish and Wildlife. Bleckmann, H., Mogdans, J., Engelmann, J., Kröther, S., & Hanke, W. (2004). Das Seitenliniensystem. Wie Fische Wasser fühlen. Biologie in unserer Zeit, 34(6), 358–365. Costa, M. J., Fuentes-Pérez, J. F., Boavida, I., Tuhtan, J. A., & Pinheiro, A. N. (2019). Fish under pressure: Examining behavioural responses of Iberian barbel under simulated hydropeaking with instream structures. PloS one, 14(1), e0211115.

Literature

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Deutsche Vereinigung für Wasserwirtschaft, Abwasser und Abfall e. V. (2005). Fischschutzund Fisch-abstiegsanlagen – Bemessung, Gestaltung, Funktionskontrolle. Hennef. Deutsche Vereinigung für Wasserwirtschaft, Abwasser und Abfall e. V. (2014). Merkblatt DWA-M 509: Fischaufstiegsanlagen und fischpassierbare Bauwerke – Gestaltung, Bemessung, Qualitätssicherung. Hennef. Europäisches Parlament und Rat der Europäischen Union. (2000). Richtlinie 2000/60/EG des Europäischen Parlaments und Rates der Europäischen Union vom 23. 10. 200 zur Schaffung eines Ordnungsrahmens für Maßnahmen der Gemeinschaft im Bereich der Wasserpolitik. Amtsblatt der Europäischen Gemeinschaften L 327/1–327/72 vom 22.12.2000. Gough, P., Philipsen, P., Schollema, P. P., & Wanningen, H. (2012). From sea to source: International guidance for the restoration of fish migration highways. Regional Water Authority Hunze en Aa’s. Ministerium für Umwelt und Naturschutz, Landwirtschaft und Verbraucherschutz des Landes Nord-rhein-Westfalen. (2005). Handbuch Querbauwerke. Klenkes. Larinier, M., Travade, F., & Porcher, J. P. (2002). Fishways: Biological basis, design criteria and monitoring. Bulletin Français de la Pêche et de la Pisciculture, 354. Lucas, M. C., & Baras, E. (2001). Migration of freshwater fishes. Blackwell Science. Schwevers, U., & Adam, B. (2020). Fish protection technologies and ways for downstream migration. Springer Nature. Silva, A. T., Lucas, M. C., Castro-Santos, T., Katopodis, C., Baumgaertner, L. J., Thiem, J. D., Aarestrup, K., Pompeu, P. S., O’Brien, G. C., Braun, D. C., Burnett, N. J., Zhu, D. Z., Fjeldstad, H.-P., Forseth, T., Rajaratnam, N., Williams, J. G., & Cooke, S. J. (2018). The future of fish passage science, engineering, and practice. Fisch and Fischeries, 19(2), 340–362.

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Philosophy and Method Specialist Discipline Ethohydraulics—How Does it Work?

Introduction Ethohydraulic investigations focus on observations of aquatic animals under varying environmental conditions, most typically carried out in hydraulic engineering laboratories. From these observations, characteristic behaviours and their causes are derived as findings. The findings must be carefully validated for practical use and depending on the application, can then be transferred into engineering design, planning best practices and dimensioning guidelines for hydraulic structures. Furthermore, ethohydraulic studies can also contribute to the definition of habitat requirements for aquatic animals in the form of measurable limits and threshold parameters, even considering social interactions in the form of qualitative observations (e.g. presence or absence of swarm behaviour). In order to observe the changing behaviours of aquatic organisms as a response to complex environmental conditions, it is necessary to simulate these conditions in controlled laboratory experiments. The ethohydraulic knowledge gain results from the fact that repeatable, behavioural-biological findings can be correlated with physical measurement data during experimentation, creating practical recommendations which can be transferred into practice. Ethohydraulic studies follow a straightforward methodology with three main phases, interconnected by coupling procedures (Fig. 2.1). The phases of ethohydraulics are Pre-Analysis, the Ethohydraulic Test and Transfer, and are linked via the intermediate steps Situational Similarity and Ethohydraulic Signature. The remainder of this chapter explains each of the three individual steps and their couplings. A detailed presentation of the methodology and applications can be found in the full textbook on Ethohydraulics (Adam & Lehmann, 2011).

© Springer Fachmedien Wiesbaden GmbH, part of Springer Nature 2022 B. Lehmann et al., Ethohydraulics, Springer essentials https://doi.org/10.1007/978-3-658-35416-9_2

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Fig. 2.1 The three phases of ethohydraulics (top) for field (bottom left) and laboratory (bottom right) studies

2.1

Phase 1: Preliminary Analysis

Ethohydraulic studies are most commonly carried out as large-scale laboratory tests. This is because the boundary conditions such as the upstream and downstream water levels can be held constant during the test period, and the test procedure itself is in most cases easily visible and can be recorded using video cameras and standard flow measurement equipment. Due to size restrictions, the hydraulic conditions occurring in real hydraulic structures and natural water bodies cannot be fully reproduced in a laboratory. Therefore it is key to always consider that even large physical laboratory experiments are ethohydraulic approximations of the wider spectrum of conditions a wild organism experiences in nature. Preliminary analysis is needed before beginning lab experiments to ensure that the physical conditions affecting the aquatic organisms are simulated as closely as possible in the laboratory model. In addition to reproducing the hydraulic situation and other stimuli from the environment, animals of different species and sizes should be allowed to react in the test rig with quasi-natural behaviour—i.e. by ensuring that they have enough available space. An important part of preliminary analysis is to carefully establish whether and to what extent the hydraulic situation in question can be represented in a partial model. Furthermore, it must

2.1 Phase 1: Preliminary Analysis

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also be determined to what extent the real situation can be abstracted for the ethohydraulic investigation. The necessary data can be gathered using field measurements as well as numerical models in order to assess the range of hydraulic conditions which are expected to occur in the field. In cases where data collection and modelling are not feasible, it is best to review previous studies with similar conditions in order to provide an order of magnitude estimate of the physical conditions expected (e.g. flow depths, velocities, turbulence) and the behavioural response of the aquatic organisms to those conditions. The preliminary analysis step illustrates the transdisciplinary nature of ethohydraulics, as both flow and biological requirements must be considered in the first stage of hydraulic model development, which requires some specific knowledge of species and behavioural biology in order to proceed to the laboratory experiments (Fig. 2.2). The first step in preliminary analysis is to hypothetically define the flowbehaviour conditions (qualitative or descriptive) which are to be investigated. Those specific parameters which can be recorded and evaluated must then be

Fig. 2.2 Preliminary analysis steps to achieve situational similarity between the natural and model situations relevant to the study

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compiled. The most common are geometric parameters such as the width, sediment grain size and water depth, hydraulic parameters such as minimum, mean and maximum flow velocity and ecological requirements such as the presence and type of bed structure, light conditions, water quality and temperature. For each particular study, the identified conditions should then be ranked in terms of their assumed significance. As an example, a hypothesis can be formulated that the water depth and sediment grain size have a higher relevance for resting aquatic animals than the water quality parameters and ambient lighting. Once the conditions are ranked and relationships between them are prioritized, planning can begin on the laboratory model to create an experiment which is as close to nature as possible. Additional conditions are deliberately neglected or only represented in a simplified form in the laboratory model; for example, keeping the water temperature constant throughout all experiments. Example: Rocky Channel for Fishpassage

Ethohydraulic laboratory tests were carried out to determine the design specifications of a rocky ramp fishway using large stones in order to improve fish passage. Plans for the channel including the expected hydraulic conditions (e.g. discharge, water depths) and channel geometry (e.g. slope, cross-section shape) were available from a previous study. Ethohydraulic tests were needed to evaluate both the required discharge and to dimension and place the large stones such that a flow signature with sufficient water depth was created which is attractive and passable for fish willing to migrate (Fig. 2.3, left). Due to space and resource constraints, it was not possible to reconstruct the entire rocky ramp fishway at full scale. Therefore, only a representative section of the channel was replicated at full scale in the laboratory. Situational similarity of the model was based on conditions associated with “migration corridor”, which was assigned the highest priority. The physical parameters associated with this condition included the water depth, flow velocities, stone dimensions, inter-stone distances as well as flow zones such as backflow areas, deadwater zones or strongly turbulent wake flows at the supporting stones. Other conditions such as the water quality, light conditions, and discharge fluctuations were not considered a priority for the ethohydraulic studies and were kept constant during all experiments. The laboratory model was controlled such that the water depths and discharges matched the planning data of the real rocky ramp fishway (Fig. 2.3, right). During the ethohydraulic tests in the laboratory,

2.2 Situational Similarity as a Transition

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Fig. 2.3 Rough channel with large rocks shortly before commissioning (top left) and the situationally similar laboratory partial model for ethohydraulic investigations (top right)

the fish behaviour was investigated for different arrangements of the supporting stones, and key findings were used to derive the practical specifications for the installation of large stones in a rocky ramp fishway.

2.2

Situational Similarity as a Transition

The preliminary analysis results in concrete design and operational specifications for the laboratory model. Afterwards, the next step is to carry out the ethohydraulic tests with living animals. This transition is referred to as situational similarity, and is important because it provides the means to cross-compare the prioritized physical conditions which form the basis of the laboratory study with conditions found in the field.

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Specialist Discipline Ethohydraulics—How Does it Work?

Phase 2: Ethohydraulic Tests

In the actual ethohydraulic tests, aquatic organisms of different species and sizes are taken from the field. The physical conditions and simulated scenarios are recreated in a laboratory study using a situationally similar model. Here it is also important to consider that the legal requirements for animal experiments and the keeping of laboratory animals apply, and that official permits are most likely necessary (Adam et al., 2013). During ethohydraulic testing, it is important to closely observe the behaviour of the test subjects and identify reaction patterns to the given situation. For example, exploration, avoidance, shyness or escape behaviour. In addition, it is necessary to find out which physical parameters, and at which range of values trigger an identified behaviour. The most common parameters are usually geometric dimensions, flow velocities or turbulence variables. Only those particular behaviours which occur with high frequency and in a very similar way for the different test subjects should be considered as reproducible responses. Establishing these dose–response relationships can be challengeing and time-consuming due to large number of observations needed to verify that a specific stimulus is reproducible under complex ethohydraulic test conditions (Fig. 2.4). The focus of ethohydraulic tests is to collect detailed behavioural observations as chronological recordings. This is done most easily by capturing videos during the tests from different perspectives and taking supporting photos during special situations. In this way, the documented behaviour can be evaluated in detail after the actual test. The definition of reaction zones can be especially helpful— this allows for the labelling of spatial regions of interest which are assigned to repeatable, characteristic behaviours.

Fig. 2.4 Step-wise procedure of the ethohydraulic test phase

2.3 Phase 2: Ethohydraulic Tests

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In addition to reaction zones, the counting of observed events and their statistical analysis can be useful for correlating findings derived from behavioural observations. However, event analyses without behavioural observations should not be considered as a substitute for detailed behavioural observations. This is because the underlying behavioural dynamics themselves are often not possible to be counted as simply local events due to memory effects (e.g. the physical conditions and behavioural responses of the previous five minutes may condition the individuals current response). Considering behavioural studies in general, it is important to keep in mind that the number of available subjects and trials is usually not sufficient for event-based inferential statistics (Böckmann, 2020). This is further illustrated with an example in Sect. 3.1. Example: Determining Reaction Zones for a Bypass Channel

Ethohydraulic investigations were carried out to test the design and function of a protective rack with a shallow incline. The screen guided fish into a bypass channel, which served as an artificial migration corridor for fish at a hydropower plant. The main objective of the study was to derive concrete design and operating recommendations to ensure that the bypass channel functioned properly. First, a physical model was set up in a large laboratory flume, and different boundary conditions were assigned as the priority conditions for the ethohydraulic tests including the angle of inclination, water level, inflow velocity, and bypass flume design geometry (Fig. 2.5). The fish were able to roam freely within the experimental space. Characteristic reactions and behavioural patterns were observed and recorded considering the species and their development stages within certain sections of the inclined rack bypass channel system. In order to systematically compare the observations, and to be able to synchronize them with hydrometric measurements and the experimental conditions, three reaction zones were defined: zone A extends upstream along the channel to the toe of the rack and vertically from the bottom to the water surface. In this space, the behaviour of fish approaching the inclined rack was investigated. In zone B directly at the inclined rack, the behaviour of the subjects on and above the rack surface was observed. Finally, zone C comprised the transition from the upper edge of the rack to the bypass channel; in this space it was found that fish decided whether and under which conditions they accepted the system as a migration corridor.

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Fig. 2.5 Physical model used for the ethohydraulic investigations of the inclined rack bypass channel system, showing its individual components (top row of images) and the corresponding reaction zones (bottom row of images)

2.4

The Ethohydraulic Signature as a Transition

Once a stimulus dose–response relationship has been identified from testing, the basis for transferring the ethohydraulic results to the natural situation must be established. The next step is to identify the measured parameters which most likely triggered or influenced the observed behavioural response of the animals. This constellation of identified parameters forms the basis of the ethohydraulic signature.

2.4 The Ethohydraulic Signature as a Transition

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The term “hydraulic signature” (Latin: signatum = what is drawn) itself refers to the characteristics and uniqueness of a flow phenomenon. Hydraulic signatures relevant to aquatic organisms have been identified in various physiological experiments (e.g. Liao, 2007; Lupandin, 2005) and are frequently included in habitat models using terms such as “stream habitat types” (Aadland, 1993), “hydraulic stream ecology” (Statzner et al., 1988) and “hydraulic signatures” (Coarer, 2007). In order to describe an ethohydraulic signature, geometric, kinematic and dynamic parameters which form the basis of situational similarity are most commonly used. It is worth noting that the paramters should be chosen which allow for the derivation of practically applicable measures, rules and regulations in the following transfer process. The identification and classification of the ethohydraulic signature is carried out in three successive steps: • Determine the couplings between a subjects’ behaviour and behaviourtriggering conditions, e.g., structures and currents in the regions of interest. • As many potentially influential parameters as possible are recorded by hydrometric measurements (e.g. geometries, flow phenomena such as eddy and turbulence structures and their spectra). These data, together with the behavioural data from step 1, represent the candidate ethohydraulic signature. • Behaviour-triggering observations are cross-compared with known stimulus thresholds or limit values (e.g. for the performance capacity of the animals). In this step, it is often best to visualise the parameters overlaid onto imagery and video to determine the key parameters needed to include in the final ethohydraulic diagram.

Example: Ethohydraulic Signature and Ethohydraulic Diagram for Fish Passability through a Double Slot Pass

As part of the planning of a large slot fishway around a weir, the passability of the slot flow presents a classic ethohydraulics example, especially considering weakly swimming fish. Ethohydraulic tests were conducted in a large-scale situationally similar partial model with several slot-pool configurations. In this study, the primary stimulus for the fish used in the slot passage was assumed to be the flow conditions, and the water depth and/or bed characteristics were considered to be secondary. Following the ethohydraulic diagram, the flow situation is first described in purely qualitative terms (Fig. 2.6, left). A measurement grid was defined at the immediate vicinity of a slot, and the flow

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velocities as well as their temporal fluctuations were recorded at all measurement points as velocity vectors (Fig. 2.6, right). By intersecting the measured flow values with fish species-specific swimming performance values, ethohydraulic diagrams can be created to compare and optimize the geometries and flow conditions of the partial models (Fig. 2.6, bottom right).

Fig. 2.6 The overlay of qualitative flow signatures (left) and flow velocity measurements (top right and middle) create a unique ethohydraulic diagram indicating the swimming speed regions of fish during passage (bottom right)

Literature

2.5

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Phase 3: Transfer

By intersecting fish reaction behaviour patterns with either individual parameters or parameter combinations, it is possible to draw conclusions from the ethohydraulic laboratory investigation to the corresponding natural situation. If situational similarity is guaranteed, it can be assumed with high probability that the studied individuals will react to the same stimuli or stimulus constellations in the field in a similar way to the laboratory experiments. The ethohydraulic transfer process can be applied to establish new design criteria, physical thresholds and qualitiative rules: • Transfer of ethohydraulic findings for the design of special hydraulic engineering facilities (e.g. fishways, bypasses) considering local boundary conditions; • Transfer of ethohydraulic findings into physical thresholds (e.g. maximum swimming speeds) which can be used to cover a broad range of hydraulic engineering measures; • Transfer of ethohydraulic findings into qualitative rules (e.g. initiation of rheotaxis), which should be used in planning or revising hydraulic engineering measures as far as possible. The validation of laboratory findings using field tests should be considered as a key element of the transfer process, even if this demands significant additional effort. The use of modern telemetry and sonar techniques as well as novel measuring probes play an important role in ethohydraulics and are presented in detail in Chap. 4.

Literature Aadland, L. P. (1993). Stream habitat types: Their fish assemblages an relation-ship to flow. North American Journal of Fisheries Management, 13, 790–806. Adam, B., & Lehmann, B. (2011). Ethohydraulik – Grundlagen, Methoden, Erkenntnisse. Springer. Adam, B., Schürmann, M., & Schwevers, U. (2013). Zum Umgang mit aquatischen Organismen. Springer Spektrum. Böckmann, I. (2020). Entwicklung eines Verfahrenskataloges für statistisch abgesicherte ethohydraulische Forschungen. In Technische Universität Darmstadt (Hrsg.), Mitteilungen des Instituts für Wasserbau und Wasserwirtschaft, 157. https://doi.org/10.25534/tup rints-00011586.

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Coarer, Y. L. (2007). Hydraulic signatures for ecological modelling at different scales. Aquatic Ecology, 41, 451–459. Liao, J. C. (2007). A review of fish swimming mechanics and behaviour in altered flows. Philosophical Transactions of the Royal Society B Biological Sciences, 362, 1973–1993. Lupandin, A. I. (2005). Effect of flow turbulence on swimming speed of fish. Biology Bulletin, 32(5), 461–466. Statzner, B., Gore, J. A., & Resh, V. H. (1988). Hydraulic stream ecology: Observed patterns and potential applications. Journal of the North American Benthological Society, 7(4), 307–360.

3

Examples from Practice Ethohydraulic Findings—What Do They Mean?

Introduction Behavioural observations with animals generally require considerable amounts of patience and attention. Especially at the beginning of ethohydraulic experiments, it is more often then not the case that fish will have unexpected responses to the test environment. It is not uncommon that observations do not initially appear to yield the key findings needed to conclusively address the research questions. Reproducible behaviours can be found only after repeated experiments with the same experimental setup and boundary conditions or after completing comparative tests with only a single experimental parameter. Such behaviours follow the same pattern, and can be safely interpreted as the expected response to the respective situation. In order to obtain reliable findings suitable for transfer to the field, careful experimental design is necessary as well as the consistent adherence to the methodological standards established in Adam and Lehmann (2011). In order to avoid mistakes in the design phase, we provide an overview of the most frequent pitfalls to illustrate how to implement practical ethohydraulics findings in hydraulic engineering projects.

3.1

The Pitfalls of Ethohydraulics

Observing Versus Counting The way ethohydraulic tests are conducted and evaluated influences the findings and can lead to misinterpretations. The risk of false conclusions is particularly high if the focus of the observational method is on the counting of events, e.g. the number of fish observed to swim through an opening, versus the number of fish who did not. Another example of such count-based misinterpretation is also presented by Amaral © Springer Fachmedien Wiesbaden GmbH, part of Springer Nature 2022 B. Lehmann et al., Ethohydraulics, Springer essentials https://doi.org/10.1007/978-3-658-35416-9_3

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Fig. 3.1 Setup used in Amaral et al. (2003) to investigate the effectiveness of a rack set at an angle of 45° to the incident flow with a bar spacing of 25 mm (graph modified from Amaral et al., 2003)

et al. (2003) on an angled rack (Fig. 3.1). Such racks are used at many sites in the United States to direct salmon smolts to a bypass positioned at the downstream end. The purpose of this study was to determine whether this guiding effect also occurs in American eels of the species Anguilla rostrata. Evidence was provided by comparing the counts of experimental fish trapped at two different locations: a catch bag and box located behind the rack and, a catch box located downstream of the bypass opening. As eels are known to be crepuscular and nocturnal, all laboratory tests were conducted in the evening hours. No behavioural observations were made, and each morning the number of eels contained in the two fish traps was counted. The catch box behind the bypass contained considerably more eels than the trap behind the rack. The authors published their recommendation that bypasses should be positioned at the downstream end of angled racks. In Europe, angled racks referred to as “guide racks”, were recommended to ensure eel migration (Ebel, 2013 et al.). It was not until several years later that the statements of Amaral et al. (2003) were revised, after renewed ethohydraulic tests and field studies in the USA revealed that there was actually no effect of angled racks for eel guidance (Electrical Power Research Institute [EPRI], 2016). The root cause of this unfortunate misunderstanding of study results lies both in the experimental set-up and the evaluation method of the initial investigation. First, the majority of the eels used were large and physically unable to pass through the 25 mm rack. Regardless of how frequently they swam up to the rack during the night, they were unable to pass through it and consequently could not get into the catching device located behind it. The bypass opening, on the other hand, needed only to be

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passed once in order to be detected in the downstream trap. Therefore most eels were contained in the catch box at the end of the bypass in the morning. As counts without supporting visual observations were carried out, the causal relationship between eel swimming behaviour at the rack and the detectability of the bypass opening could not be correctly defined. In Germany, comparable ethohydraulic studies on the guiding effect of angled racks had been carried out in the laboratory channel of the Technical University of Darmstadt in the late 1990s. Direct visual observations indicated that European eels (Anguilla anguilla) cannot be guided by an angled rack (Adam et al., 1999). However, the reasons for the failure of this constellation for the eels were still not fully understood at that time. It was not until 15 years later that the first comparative ethohydraulic studies on the behaviour of different species on an angled rack provided final clarity (Lehmann et al., 2016). These studies revealed that the fundamental differences in behaviour depend on the type of locomotion (Fig. 3.2, Bone & Marshall, 1985): • Most native species, for example salmonids, perches and carps (Salmonidae, Percidae and Cyprinidae), belong to the so-called subcarangiform locomotion type. They move by powerful strokes with their caudal fin. • Species of the anguilliform locomotion type, on the other hand, generate their propulsion through sinuous body movements supported by one or more fin seams.

Fig. 3.2 Locomotion types (graph modified after Hoar & Randall, 1978)

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Fig. 3.3 Setup for ethohydraulic tests with anguilliform and subcarangiform species on an angled rack; the bypass opening is located to the right of the angled rack

These species, which in addition to the eel also include lampreys (Petromyzontiformes), catfish (Silurus glanis) and burbot (Lota lota), can swim both forwards and backwards, but this propulsion method generally generates less thrust force, and the attainable swimming speeds are typically significantly lower when compared to subcarangiform species. The ethohydraulic tests by Lehmann et al. (2016) were carried out with a rack set at an angle of 18° to the inflow with horizontal rack bars (Fig. 3.3). The rack bar spacing was 12 mm, small enough so that the test subjects were not able to pass through. At this rack, eels showed exactly the same behaviour as already described by Adam et al. (1999) for racks oriented perpendicular to the flow direction. The eels were observed colliding with the rack during migration, then reversing their direction, aligning themselves against the flow and fleeing the rack by returning upstream to the incoming flow (Fig. 3.4). However, eels only succeed with their reversal reaction if the incident flow velocity, vA in front of the rack, was less than 0.5 m/s. At higher velocities, “impingement” occurs, in which the eels are pressed against the rack surface by the force of the incoming flow and lose their ability to escape due to the limits placed on them by anguilliform swimming. In the field, this means that impinged fish that do not have the power to escape impingement and flee upstream die as a result of internal injury, exhaustion, or the rack cleaning machine (Fig. 3.5, left). Another key observation

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Fig. 3.4 Reversal reaction of an eel after its collision with a rack

Fig. 3.5 Impingement of an eel at an approach velocity vA = 0.8 m/s (left, modified after Adam et al., 1999) and subcarangiform fish in the same situation (right, modified after Schwevers & Adam, 2020)

was that searching behaviour over the rack surface, was not observed by European eels, nor by the other species of the anguilliform locomotion type. In contrast, species of the subcarangiform locomotion type were observed to consistently position themselves positively rheotactically aligned upstream of the rack surface and avoided impingement (Fig. 3.5, right).

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Although these fish did not perform any recognized specialized swimming maneuvers, they moved slowly along the surface of the angled rack towards a bypass opening located at the downstream end. The term “yawing” was coined by Lehmann et al. (2016) for this type of guided swimming, which was used in a similar way by Schiemenz (1957). This term is used in shipbuilding and aviation to describe comparable rotational movements of a hull around its vertical axis. As a result of yawing, a hydrodynamic pressure difference arises between the side of the fish body facing the current and the leeward side, facing away from the current. This orientation causes a net force on the body perpendicular to its longitudinal axis, propelling the swimmer without active locomotion (Fig. 3.6). The course of ships and aircraft is also affected by yaw, when water or air currents act obliquely on the longitudinal axis and cause them to drift laterally; “trimming the rudders” compensates for such yaw effects. Anguilliform species are largely unable to rapidly incline their body axis and consequently changing their position along an angled rack towards a downstream bypass opening can be difficult and in some cases, impossible. As a result, angled

Fig. 3.6 Principle of yawing for subcarangiform fish in front of an angled rack by slightly rotating their body vertical axis to the inflow (modified after Lehmann et al., 2016)

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racks are unsuitable as hydraulic guidance measures for bypass openings to be used by eels and other anguilliformes. The focus of ethohydraulics is the direct observation of events. The knowledge gain results primarily from the observation, documentation and analysis of animal behaviour, with a focus on determining repeatable reactions to the hydraulic and structural conditions in the laboratory and field environments. In order to move beyond purely descriptive or anecdotal observations of animal behaviour, controlled and repeated experiments as well as comparative studies are carried out, in which only a single parameter is systematically changed and/or individuals of different species are used. Video recordings can often supplement direct visual observations for documentation purposes, but should not be considered as replacements for them: cameras are focused on comparatively small sections of the test setup, and they cannot capture the entirety of the test environment. Whenever possible, direct observations by trained staff should be preferred because behavioural reactions may be distributed over different areas of the test environment which are not covered by video analysis. If the evaluation of ethohydraulic tests must be reduced to countable events, it should be recognized that detailed behavioural insights will be missing from the study. Determination of key causal relationships between the hydraulic situation and the behaviour of the individuals can be rendered unlikely or impossible, and the risk of misinterpretation will increase correspondingly. The Limits of Situational Similarit A decisive factor for the utility of ethohydraulic findings is compliance of situational similarity with field conditions (see also Chap. 2). A full-scale model is optimal, and can be readily implemented to investigate the passability of fishways, the acceptance of bypass openings or the reactions of fish and other aquatic animals to hydraulic, visual and in some cases, acoustic stimuli. In many laboratory studies, “partial models” are constructed which represent a specific area of the field situation relevant for the behaviour at full scale. In studies where very large areas to be represented, reduced scale models are possible. However, it should be recognized that the hydraulic conditions may not correspond to the field scale situation, and the reduced conditions may substantially influence the behavioural response. This is particularly true for the water depth, which in many cases cannot be simulated at full scale in a laboratory channel. Experience has shown that pelagic and even surface-oriented species prefer to remain close to the channel bottom in shallow water depth tests; their behaviour thus does not correspond to the situation in the field with deeper waters. Consequently, findings from the model channel on the guiding effect of near-bottom structures on pelagic species, as described in Flügel

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et al. (2015) may include behavioural responses which are not directly transferrable to field applications. Finally, it should be noted that the use of small fish species or juveniles to compensate for a physical scale reduction of the test setup is never appropriate. This is because the sensory systems, physiology, behaviour and physical performance of smaller individuals cannot be rescaled to other species and / or life age stages. All living organisms must be therefore considered only at their full physical scales during ethohydraulics tests. Behaviour is Interaction Behaviour is not only a reaction of the animal to the environmental conditions, animals also interact with each other. For example, many fish species join together to form shoals, in which individuals of the same and even mixed species often associate with each other. When swimming as part of a shoal, fish often behave very differently than when swimming alone as an individual. If ethohydraulic tests are carried out with only a small number of test specimens, because a statistical evaluation of individual events is to be carried out, it should be recognized that the lack of social interactions may skew the findings. This risk is comparatively low for species or developmental stages with solitarily behaviour, such as pike or brown trout. However, the situation becomes quite different for salmon smolts, which are frequently aggregate during ethohydraulic laboratory studies as well as during migration in the field. The particular shoaling behaviours are often largely determined by individual specimens. For example, Lehmann et al. (2016) observed that individual salmon smolts temporarily become “guard fish”, preventing conspecifics from passing bypass openings with biting attacks (Fig. 3.7). This behaviour has a direct influence on the passage rates, so that no situational similarity with isolated individual specimens is possible, and calls into question the transferability of findings to field studies using solitary individuals.

3.2

Ethohydraulic Findings for Hydraulic Engineering Practice

In the following, two examples are presented to explain the procedure of ethohydraulic investigations and to demonstrate the practical applicability of the findings.

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Fig. 3.7 “Guard fish” in front of a bypass opening in the test rig, preventing the passage of conspecifics

Example: Influence of Light in Flow Corridors on the Movement Behaviour of Fish

Many watercourses are channelized, piped or fed into culverts. Fishways and bypasses are built to facilitate free fish migration, and often must be constructed underneath or through existing infrastructure due to limited space. These artificially dark migration corridors can be partially compensated using viewing windows, which are also sometimes installed to record the ascent or descent with video cameras, and to provide the public with a first-person view of fish migration. It remains an open challenge to determine how darkening, lighting and providing high contrast environments affect the location and migration patterns of native, wild fish. Recommendations from the literature in this regard have been contradictory (Hütte, 2000; Schwevers et al., 2004; Sellheim, 1996; Vordermeier & Bohl, 2000 and others). Considering the knowledge gaps on the effects of lighting on fish migration, ethohydraulic tests were carried out in the hydraulic engineering experimental laboratory of the Technical University of Darmstadt as part of the project “Influence of light conditions on the efficiency of fishways at hydropower plants” (Engler & Adam, 2020).

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Preliminary analysis and situational similarity: to establish situational similarity, field measurements were first carried out at two tunneled fishways on the High Rhine and at an illuminated monitoring station on the Lahn, where flow velocity as well as brightness were determined at different water depths and at different times of day (Fig. 3.8). On the basis of these reference values, a 15 m long section of the laboratory flume was completely darkened with a tent (Fig. 3.9). The interior of the tent was equipped with 4 dimmable light fields (Fig. 3.10), each of which was

Fig. 3.8 Different light conditions in fishways

Fig. 3.9 Tent-enclosed section of the laboratory flume with variable lighting conditions (length 15 m)

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Fig. 3.10 Experimental settings with decreasing (top) and increasing (bottom) illuminance in the flow direction

separated from the others by a black tarpaulin extending to the water surface. The light fields were operated with illuminances of 0, 12.5, 125 and 1250 lx and could also be switched off completely. Ethohydraulic tests: for each test, illuminance of the light fields was varied. For example, either decreasing or increasing brightness was provided in the flow direction. Alternating illuminance between darkened and maximally illuminated channel sections was also tested to examine fish response to strong contrasts. In addition, tests were conducted under varying flow conditions up to a mean flow velocity of 0.7 m/s. Finally, fish were initially released in the test stand upstream as well as downstream. Each test lasted 30 min and were carried out with fish in groups of 40 to 50 subjects: • potamodromous mixed-species groups of the species barbel (Barbus barbus), chub (Squalius cephalus), gudgeon (Gobio gobio), nase (Chondrostoma nasus), roach (Rutilus rutilus), bleak (Alburnus alburnus), catfish

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(Silurus glanis), ruffe and perch (Gymnocephalus cernua and Perca fluviatilis), • single species shoals consisting of adult European eels (Anguilla anguilla); • smolts of Atlantic salmon (Salmo salar) with a length of approx. 15 cm. Findings and transfer: a total of 90 individual tests were carried out with different lighting scenarios. For most species, the chosen experimental design did not reveal any evidence that light has a significant influence on locomotion. Also, contrary to the literature (Gosset & Travade, 1999; Larinier & BoyerBernard, 1991a, b), salmon smolts responded primarily to flow conditions in the experimental setup, exhibiting little preference across the tested lighting conditions and did not have a noticeable reaction to the alternated patterns of lighting. Similarly, European eels tested in this study did not behave strongly, and were not found to be “light-shy” as described in the literature (including Hadderingh et al., 1999; Lowe, 1952). It was observed however, that some eels preferred to stay in the darkness at low flow velocities up to 0.25 m/s. At flow velocities greater than 0.5 m/s, the eels were evenly distributed across all channel sections independently of the illuminance (Fig. 3.11). During these studies the catfish was observed to be light-shy under all tested configurations, and retreated frequently into the darkened areas (Fig. 3.12). These ethohydraulic findings suggest that for the species and age stages tested within flow corridors, lighting plays a subordinate role in movement behaviour. Therefore, providing artificial lighting that matches natural lighting conditions does not appear to be necessary to ensure passability of tunneled and culverted stream segments and fishways. Concerns that brightly lit observation stations may have a detrimental effect on migration activities were not found to be substantiated. Therefore, in the context of field transfer, special

Fig. 3.11 Nearly uniform distribution of eels at a flow velocity of 0.5 m/s in the channel sections with 12.5 lx (left), 125 lx (middle) and 1250 lx (right) (the flow direction is from right to left)

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Fig. 3.12 Catfish preference for illuminated channel sections at different flow velocities

lighting of migration corridors may not be necessary, provided that the situational similarity of all other parameters is considered during the transfer phase of the ethohydraulic study. Example: Development of a Chinese Mitten Crab Guidance System

The applicability of ethohydraulics is not limited solely to fish, and the behaviour of invertebrates can also be analysed using this method. The need for behavioural studies of the Chinese mitten crab (Eriocheir sinensis) arose from the fact that millions of juveniles of this exotic species, introduced to Central Europe some 100 years ago, migrate upstream every year from the Elbe estuary. After travelling some 140 km during their migration, the crabs arrive at the Geesthacht weir, where their migratory activities block the monitoring facilities of the fishways (Fig. 3.13). In order to maintain the passability of the fishways and carry out monitoring, it was necessary to develop a robust system against the migrating mitten crabs, which are up to 8 cm in size and one to two years old. Although several past efforts had been made to create traps and barriers for mitten crabs (Fladung, 2000; Meyer-Waarden, 1954; Panning, 1938; Schiemenz & Koethke, 1935), there remained very limited knowledge about the behaviour of these crabs. To address this knowledge gap, ethohydraulic investigations with 900 juvenile mitten crabs took place in 2011 in two experimental stations of the hydraulic engineering laboratory of the University of Karlsruhe (Ballon & Adam, 2016).

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Fig. 3.13 Juvenile mitten crabs during a mass migration in a fishway

Preliminary analysis and situational similarity: the first ethohydraulic study was designed as a “flow funnel” in which the flow velocity was successively increased, and the crabs’ upstream migration path was directed directly against the flow (Fig. 3.14). Similar to the fish passes at the Geesthacht weir, the bottom of the test site was covered with boulders and coarse stones of class CP90/250 (90–250 mm stone diameter) at 1:1 scale. With an inflow of 180 l/s and a water depth of 0.4 m, a flow velocity of 0.45 m/s was achieved over the rough bottom at the downstream end. The wide end of the flow funnel decreased linearly to the upstream end, which had a maximum velocity of 2.15 m/s in the narrowest section. These higher values corresponded to those in the fishway. The second set of ethohydraulic tests were carried out in a conventional laboratory flume, in which several situationally similar barriers with slit-shaped passages were implemented. These were solid trashracks of triangular, round or rectangular bars with a thickness of 50 mm and spacing of 15 mm, each rising 30 cm above the bottom. These racks were designed to stop migrating mitten crabs (Fig. 3.15) without hindering the passage of migrating fish, especially bottom-oriented species. The near-bed properties and hydraulic conditions were situationally similar to those found in the field. Ethohydraulic tests and findings: behavioural observations revealed that mitten crabs only swim in standing water and over short distances. As soon

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Fig. 3.14 Schematic of the “flow funnel” built specially for the ethohydraulics lab investigation

Fig. 3.15 Types of racks tested to determine the most suitable type of barrier

as a current is present, they move sideways upstream, pulling and pushing their body laterally against the current. In doing so, the tapered end-limbs of their legs find a secure hold onto the surface, and a single leg is sufficient

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to hold their entire body and propel it upstream. Up to flow velocities of 1.4 m/s, the crabs expose themselves directly to the current. At higher flow velocities, they move upstream and nestle closely to the substrate using their flat body structure. If the crabs should encounter an obstacle, they first try to squeeze past it, and if they do not succeed, they then attempt to climb over the obstacle. Basic racks were also overcome in this way, provided that the crabs were able to grasp the elements with their extremities. In the case of the triangular and rectangular rack elements, they were able to do this with little difficulty. However, it was observed that round bars could not be used by the crabs for support. Since the span of the extremities of juvenile mitten crabs reaches up to 30 cm, the height of a migration obstacle must exceed the roughness peaks of the substrate by at least 30 cm to prevent them from climbing over the obtacles. The migrating crabs can still accumulate in front of an obstacle in a pile, allowing groups of them to overcome 30 cm high obstacles. In this way, mitten crabs in large numbers can overcome such obstacles in cases where a single individual cannot. It is not sufficient to simply stop the mitten crabs, instead they must be diverted through and out of the system. To this end, climbing aids were specially adapted to the crabs’ locomotion abilities. A crab guidance system was constructed with 40 cm wide migration corridors made of 10 mm mesh wire, which was constrained using very smooth surfaces such as sheet metal or Plexiglas. These migration corridors allow the crabs to be guided above the water surface and fed into tubes lined with 10 mm mesh wire (Fig. 3.16). Using diversion tubes, the animals can be guided over long distances and in nearly any desired direction. Transfer: a mitten crab guidance system was successfully deployed on the Elbe River in a double slot pass at the Geesthacht weir to protect the monitoring facility for detecting ascending fish from the invasive crabs. The solution required installing climbing structures and diversion tubes, guiding the mitten crabs which had entered the trapping chamber into the headwater of the barrage (Fig. 3.17).

3.2 Ethohydraulic Findings for Hydraulic Engineering Practice

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Fig. 3.16 Example crab guidance system, constrained using smooth surfaces with round bars and climbing aids made of wire mesh

Fig. 3.17 Transition from a climbing structure to the diversion tube to guide mitten crabs away from the monitoring facility at the Geesthacht double slot pass

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Ethohydraulic findings—What Do They Mean?

Literature Adam, B., Schwevers, U., & Dumont, U. (1999). Beiträge zum Schutz abwandernder Fische—Verhaltensbeobachtungen in einem Modellgerinne. Natur & Wissenschaft. Adam, B., & Lehmann, B. (2011). Ethohydraulik – Grundlagen, Methoden, Erkenntnisse. Springer. Amaral, S. V., Winchell, F. C., McMahon, B. C., & Dixon, D. A. (2003). Evaluation of an angled bar rack and a louver array for guiding silver American eels to a bypass. American Fisheries Society Symposium, 33, 367–376. Ballon, E., & Adam, B. (2016). Entwicklung eines Wollhandkrabben-Leitsystems für Fischaufstiegsanlagen. Wasserwirtschaft, 106(7–8), 36–40. Bone, Q., & Marshall, N. B. (1985). Biologie der Fische. Gustav Fischer. Ebel, G. (2013). Fischschutz und Fischabstieg an Wasserkraftanlagen. Handbuch Rechenund Bypasssysteme. Eigenverlag. Engler, O., & Adam, B. (2020). Beeinflussung der Effizienz von Fischwegen durch die Lichtverhältnisse. Artenschutzreport, 41, 41–47. Electrical Power Research Institute. (2016). Laboratory Studies of eel behavior in response to various behavioral cues. Technical Report. Palo Alto. Fladung, E. (2000). Untersuchungen zur Bestandsregulierung und Verwertung der Chinesischen Wollhandkrabbe (Eriocheir sinensis). Schriften des Instituts für Binnenfischerei Potsdam-Sacrow, 5. Flügel, D., Bös, T., & Peter, A. (2015). Forschungsprojekt: Massnahmen zur Gewährleistung eines schonenden Fischabstiegs an größeren mitteleuropäischen Flusskraftwerken. EAWAG. Gosset, C., & Travade, F. (1999). Devices to aid downstream salmonid migration: Behavioral barriers. International Journal of Ichthyology, 23(1), 45–66. Hadderingh, R. H., van Aerssen, G. H. F. M., de Beijer, R. F. L. J., & van der Velde, B. (1999). Reaction of silver eels to artificial light sources and water currents: An experimental deflection study. Regulated Rivers: Research & Management, 15, 365–371. Hoar, W. S., & Randall, D. J. (1978). Fish physiology, Volume VII “Locomotion”. Academic. Hütte, M. (2000). Ökologie und Wasserbau – Ökologische Grundlagen von Gewässerverbauung und Wasserkraftnutzung. Parey. Larinier, M., & Boyer-Bernard, S. (1991a). Dévalaison des smolts et efficacité d’un exutoire de dévalaison à l’usine hydroélectrique d’Halsou sur la Nive. Bulletin Français De La Pêche Pisciculture, 321, 72–92. https://doi.org/10.1051/kmae:1991009 Larinier, M., & Boyer-Bernard, S. (1991b). La dévalaison des smolts de saumon Atlantique au barrage de Poutès sur l’Allier (43): Utilization de lampes a vapeur de mercure. Bulletin Français De La Pêche Pisciculture, 323, 129–148. https://doi.org/10.1051/kmae:1991001 Lehmann, B., Adam, B., Engler, O., & Schneider, K. (2016). Ethohydraulische Untersuchungen zur Verbesserung des Fischschutzes an Wasserkraftanlagen. In Bundesamt für Naturschutz (Hrsg.), Naturschutz und Biologische Vielfalt, 151. Lowe, R. H. (1952). The influence of light and other factors on the seaward migration of silver eel. Journal of Animal Ecology, 21(2), 275–309. Meyer-Waarden, P. F. (1954). Elektrische Sperren zur Bekämpfung von Wollhandkrabben. Der Fischwirt, 4(331–337), 357–364.

Literature

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Panning, A. (1938). Über die Wanderungen der Wollhandkrabbe. Markierungsversuche. Neue Untersuchungen über die chinesische Wollhandkrabbe in Europa. In Zoologisches Intitut und Zoologisches Museum Hamburg (Hrsg.). Mitteilungen Aus Dem Hamburgischen Zoologischen Museum Und Institut, 47, 32–49. Schiemenz, F. (1957). Ersatz des instinktmäßigen Wanderns der Fische in Fischtreppen durch das reflektorische Wandern. Z. Fischerei, NF, 6, 61–68. Schiemenz, F., & Koethke, H. (1935). Über die Wollhandkrabbe und Vorschläge zu deren Massenfang. Mitteilungen der Fischerei-Ver. Ostausgabe, 24(2/3), 25–32, 45–56. Schwevers, U., & Adam, B. (2020). Fish protection technologies and ways for downstream migration. Springer Nature. Schwevers, U., Schindehütte, K., Adam, B., & Steinberg, L. (2004). Untersuchungen zur Passierbarkeit von Durchlässen für Fische. In Landesanstalt für Ökologie, Bodenordnung und Forsten Nordrhein-Westfalen (Hrsg.), LÖBF-Mitteilungen, 28(3), 37–43. Sellheim, P. (1996). Kreuzungsbauwerke bei Fließgewässern – Gestaltungsvorschläge für Durchlässe, Brücken, Verrohrungen und Düker. Informationsdienst Naturschutz Niedersachsen, 16, 205–208. Vordermeier, T., & Bohl, E. (2000). Fischgerechte Ausgestaltung von Quer- und Längsbauwerken in kleinen Fließgewässern. In Landesfischereiverband Bayern (Hrsg.), Schriftenreihe des Landesfischerei

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Outlook Quo vadis ethohydraulics – what is the way forward?

Introduction Behavioural observations of aquatic organisms in the laboratory have a long tradition. More than 100 years ago, Franz (1910) carried out experiments on phototaxis and Steinmann (1913) investigated the rheotaxis of invertebrates, i.e. their reaction to the current, in specially constructed laboratory experiments. In the 1950s, Schiemenz (1950, 1952, 1957, etc.) continued this tradition with behavioural observations of fish at the service of hydraulic engineering: he carried out laboratory experiments on fish behaviour in currents in order to improve the design of fishways. Since then, many studies have been undertaken after which it was found that the findings obtained in the hydraulic engineering laboratory were not transferable to the field. For example, Taft (1986) reports on a variety of methods for protecting migrating fish that proved effective in the laboratory but failed more or less completely in the field. The results obtained in the laboratory at that time were simply not transferable to the physical conditions found in the watercourse. Against this background, the development of ethohydraulics in 2008/2009 represents an important milestone because it marks the development of a systematic approach to ensure situational similarity of laboratory investigations with those found in the field. Furthermore, ethohydraulics allows for the implementaton of key findings via transfer to real-world hydraulic engineering practice. Since its conception, the application of ethohydraulics has been substantiated in projects where the transferability of laboratory findings have been guaranteed in cases where the methodology are consistently observed. Superficially, ethohydraulics has become established as a new methodological approach. In German-speaking countries, the term has become a part of the relevant technical vocabulary, and English-language publications have increasingly begun using the term “ethohydraulics”. Ethohydraulics is taught and practiced at several universities, for example in Aachen, Darmstadt, Karlsruhe, Dresden and Zurich, as © Springer Fachmedien Wiesbaden GmbH, part of Springer Nature 2022 B. Lehmann et al., Ethohydraulics, Springer essentials https://doi.org/10.1007/978-3-658-35416-9_4

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well as by the Federal Institutes of Hydraulics and Hydrology (BAW and BfG). However, it has proved problematic that the term “ethohydraulics” is often used for studies in which the methodological requirements are disregarded, or in which there is no intersection between ethology and hydraulics at all. Accordingly, it is important to adhere to the methodological standards; this ensures the transfer of meaningful findings to the field under natural environmental conditions, which provides the basis for further development and applications of the method.

4.1

Possibilities and Limits of Statistical Evaluation

The statistical validation of study findings, which is common in most natural science and engineering disciplines, does not commonly take place in ethohydraulics. The reason for this is that the behavioural response of animals to the hydraulic and geometric conditions in the laboratory and in the field typically involves multi-scale processes with large degrees of freedom; recorded observations of individual events are often not useful or meaningful when tabulated as “counts” and statistically evaluated. The primary criterion for the validity of ethohydraulic findings is reproducibility: if the test subjects show the same reaction to a certain experimental constellation in repeated experiments, then this is a reproducible stimulus–response pattern. If such a pattern has been identified, it can be reasonably assumed that the animals will behave in a comparable manner under situationally similar conditions in the field. Regardless of this, it increases the acceptance of ethohydraulic findings if appropriate statistical validations are conducted. Prerequisites for this, however, are a “translation” of the observed behaviours into countable events and a sufficiently large number of individual values for conclusive statistics, for which Böckmann (2020) has compiled special recommendations and case-specific methods.

4.2

Possibilities of Measurement and Observation Techniques

Hydrometric measurement Various instruments have been established for the qualitative and quantitative recording of hydraulic signatures (Fig. 4.1). Despite the different methods, all measuring instruments have in common the focus on the hydraulic parameter velocity. It is worth noting that there are a great number of parameters which can be used to

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Fig. 4.1 Established measuring devices for laboratory and field use for recording flow velocities

describe a flow signature (e.g. turbulence structure, flow path contours, pressure), which can be determined qualitatively and if necessary, also quantitatively from the interpretation of measured data. For simple, point measurements of the flow velocity most commonly use hydrometric measurements from a propeller or the somewhat more robust magneticinductive probe. With this, initial statements about the average velocity in one spatial direction can be made quickly. However, if the velocity field is to be determined as different spatial components over a defined measurement grid, an Acoustic Doppler Velocimeter (ADV) is recommended. According to the current state of the art, this

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is the most common measuring instrument for laboratory investigations to record the velocity three-dimensionally within a small measuring volume at the centimeter scale. Due to the high temporal resolution of the measured values, in some cases, turbulent fluctuations in the velocity can also be analyzed. The Acoustic Doppler Current Profiler (ADCP), which is based on the same measuring principle, simultaneously measures the instantaneous velocity in defined cells of a complete measuring vertical; in one, two or three dimensions, depending on the device. This offers advantages, especially for large water depths and wide measurement cross sections, which is why it is primarily used in the field. In order to describe flow in a qualitative manner, additional measurement instruments can also be used. In the simplest case, a “thread harp” is used, where threads align themselves along the path lines of the water when immersed by the flow, and depending on the arrangement and density of the threads, the flow field can visualized with little technical effort. Dyes can also be used to visualize the flow as tracers, and complex vortex structures can be seen by the naked eye without the use of complex equipment. Particle Image Velocimetry (PIV) can achieve extremely high temporal and spatial resolution of the flow within a defined plane, and records the velocity by observing the particle displacement within the flow. By recording the area under investigation with a high-speed camera, the directions of movement of particles (often special seeding material) and the temporal and spatial offset between the individual camera images can be analyzed. One major benefit of PIV is that zones of high vorticity can be detected and measured with high resolution. In order to keep the measurement duration within tolerable ranges for large investigation areas, it is possible to create a three-dimensional hydrodynamic-numerical model. Measurement data are then needed to calibrate and validate the numerical model, which can provide detailed flow parameters within the region of interest. Detailed information on suitable flow measurement methods, numerical flow models as well as the visualization of measurement and simulation data are abundant in the corresponding technical literature (Boiten, 2008; Martin, 2011; Morgenschweis, 2010 et al.). It is important to recognize that flow parameters recorded or simulation, and their visual representations cannot replace the animals’ perception of their environments. Fish, for example, have the ability to perceive the flow at extremely high precision and resolution with their lateral line organ. This information is processed not in isolation, but rather in coordination with many other stimuli, which the animals take in as a combination of sight, taste, hearing and touch, creating a highly complex image of the underwater environment.

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Multi-parameter measurements In order to gain a better understanding of fish behaviour, new measurement techniques are being developed which more closely map the animal’s sensory experience using multi-parameter data (Fig. 4.2). One special feature of these devices is that several parameters can be recorded simultaneously and synchronously by means of various probes and biologgers, which are also perceived by fish. The measurement data can reflect external stimuli, e.g. through abiotic environmental influences, and can also represent a measurable state such as total body acceleration and link it to an observable reaction of the animal to repeatable hydraulic environments based on situational similarity. Fish sensory sondes (FSS) mimic the body geometry and proprioceptive and flow sensory systems of real fish, collecting high-resolution data from multiple pressure, acceleration, rotation, and magnetic field sensors (Fig. 4.3; Costa et al., 2019; Tuhtan

Fig. 4.2 To support ethohydraulic investigations in the laboratory and in the field, multiparameter data can be measured synchronously with new types of probes and biologgers

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Fig. 4.3 Principle of fish sensory sondes (FSS): recording the total body motion (proprioception) and fluid-body interaction (flow sensing). The FSS with their fish-like geometries can provide more detailed information about how fish’s bodies interact with the flow field in both laboratory and field investigations

et al. 2016, 2018a). Another possibility is the use of biologgers. These small devices are attached either externally to the test subjects or are implanted into the body cavity. They continuously record information about the physiology and movement of the test subject during experiments and can also capture hydrodynamic data of the environment (e.g. Brijs et al., 2019; Tuhtan et al., 2018b). However, a major challenge in using biologgers is that the behaviour of the subjects can be affected as a result of the attachment/implantation. Therefore, careful preliminary and comparative testing is essential when using this method. By combining these measurement methods, it will be possible to investigate new stimulus–response patterns based on observations of fish response mechanisms and simultaneously recorded environmental data, which are not solely based on flow velocity and direction. New as well as faster and higher-resolution measurement methods lead to extensive data collection, which must first be processed for further representation and analyses. In the course of processing, the “raw sensor recordings” should always be used and initially time-synchronized. Afterwards, it is necessary to identify and remove measurement errors in the sense of outliers, for which filters and postprocessing software are available. The future holds many possibilities in terms of data acquisition and evaluation: For example, the increasing performance of computer systems can be used to employ powerful algorithms or even machine

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learning methods for complex multivariate data analysis. The use of hybrid methods which couple fish observations, probe data and numerical simulations can lead to ethohydraulic studies being more strongly supported by physical observations. Observation techniques for fish behaviour In the field of observation and analysis of fish behaviour, there are now a wealth of methods of varying accuracy to be applied depending on the problem at hand (Table 4.1). The main research objectives here are typically basic research; small-scale and large-scale behavioural analyses, quality assurance and functional testing of facilities, and fish population analyses. The observations are incorporated into the three phases of ethohydraulic investigations in different ways. Methods can be invasive or non-invasive as well as catch-dependent and catch-independent, with the aim of investigating natural animal behaviour that is as uninfluenced by the observation processes as possible. Important developments in the field of behavioural observations are briefly presented in this work. Further detailed information can be found, for example, in Lucas and Baras (2000), Schmalz et al. (2015), DWA (2005) and DWA (2014). When supported by digital cameras, the swimming paths and speeds of the test subjects can be monitored, recorded and later evaluated using photogrammetric techniques. The trajectories of individual swimming paths can help to identify preferred swimming corridors more precisely, and to analyse them in a more targeted manner by overlaying them with spatial flow signatures (Fig. 4.4). Animal transponders can be used to record the passage of animals at specific points in the experimental room over time. The transponders, also known as PIT tags (Passive Integrated Transponder), are glass-encased implants usually 12 to 32 mm long and 2 to 4 mm in diameter. They are injected under the skin or applied into the abdominal cavity of fish for individual tagging. Fixed location antennas are installed in the experimental area. When a transponder enters the oscillating circuit of such an antenna, it is energetically charged and thus activated, i.e. it transmits its distinctive multi-digit code as a signal. The antenna receives the signal and forwards it to a reader, which decodes the code. The information is then logged in a file on a PC together with the address of the antenna and the time of the read event (Fig. 4.5). PIT tags are suitable for both laboratory and field use. Example: functional control of fishways

PIT tags also allow a detailed examination of the efficiency of fishways, especially if several facilities in the same water body or at the same hydraulic

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Camera based methods

Counting

Tag and recapture

Transponder technology

Sonar technology Environmental DNA

x

Fish population analysis

Physical damage assessment by hydraulic installations

Determination of large-scale migration routes

(x) (x)

Laboratory Viewing window at field facilities Time of flight (ToF) Structured light Stereo vision Particle image velocity (PIV) Fish Traps Manual counts Electrofishing Resistive counter Automatic Laser counter counting Infrared counter systems Video counter Screenings control (dead animals) Colouring Fin clipping Individual marking Tattoos Bar codes HI-Z turb’n tag Special tags Data storage tag (DST) Passive PIT tag Radio telemetry Active Acoustic telemetry Single-beam sonar Split-beam sonar Dual-beam sonar Multibeam (imaging) sonar

Counting cross-sectional passages in the watercourse

Direct observation

Accurate tracking of swimming paths

Observation techniques for fish behaviour in the laboratory and in the field

Detailed movement analysis and swimming kinematics

Table. 4.1 List of observation techniques for fish behaviour in the laboratory and in the field; x = possible; (x) = possible under certain conditions or limited; “empty” = not possible; s = possible on a small scale or under laboratory conditions

x/s

x

x

x

x

(x) x

x

(x)

x

x x x

x x x

(x)

x

(x)

x/s

x x x x

x

x (x)

x

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Fig. 4.4 Conceptual overview of camera-based tracking methods

structure are to be investigated. As an example, eight fishways at the barrages Augst-Wyhlen, Rheinfelden, Ryburg-Schwörstadt and Säckingen in the High Rhine were investigated. At each of their entrances and exits, the fishways were equipped with antennas to track the movement patterns of some 20,000 PIT-tagged fish of different species (Schwevers et al., 2020). The study showed that it is primarily the location of the entrance in relation to the main flow in the river that determines the detectability of a fishway. In order to find fishways located far away from the main flow, the transposed migrating fish needed much more time than in the case of facilities positioned directly at the power plant at the same barrage.

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Fig. 4.5 PIT tags of different sizes (left) and sketch showing the operation of a frame antenna at the slots of a fishway (right)

The example of the detectability of fishways illustrates the key value of field studies. As a rule, multiple large-scale studies cannot be simulated similarly to the full extent of the situation using laboratory tests alone. Therefore, field studies are necessary for the evaluation of the detectability of a facility, taking into account the large-scale flow conditions and the large number of migration corridors. In the ethohydraulic laboratory model, however, near-field studies for the design of the entrance conditions can be investigated in many cases. The findings, guideline values, design specifications and recommendations obtained in this way can be validated in the field by means of biologgers and telemetry and if necessary, repeated to validate the primary findings. If telemetry is used, the behaviour in the field can be evaluated in even greater detail. Telemetry systems with active transponders consist of a transmitter (emitter) that emits a signal and a receiver (antenna or hydrophone) to detect and decode the signal (Fig. 4.6). Depending on the type of signal, telemetry systems are divided into radio telemetry and acoustic telemetry. Depending on the locating accuracy, the real swimming paths of the fish can be visualized topographically in two or three dimensions as part of the signal evaluation. Modern telemetry transmitters are so small that they can even be implanted in small fish species and juveniles, e.g. salmon smolts, as well as slender species such as eels and lampreys (Fig. 4.6, bottom left). However, the lifetime of such transmitters powered by coin cell batteries is limited to a few months. Acoustic emitters send out tone

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Fig. 4.6 Operating principles of radio telemetry (top) and acoustic telemetry (bottom)

sequences that are received by calibrated hydrophones submerged in the water body. In principle, information collected from different receivers can be intersected with each other, as with the PIT tag method, in order to reconstruct at what time a subject was in the reception area. With a sufficiently high number and density of receivers, it is also possible to document the movements of the subjects. For this purpose, the reception areas of at least three receivers must overlap in the entire study area, so that the exact position can be determined by cross bearings using triangulation. Beyond the characteristics of single, dual or split beam sonars, multibeam sonars such as DIDSON (Dual Frequency IDentification SONar) and ARIS (Adaptive Resolution Identification Sonar) can produce high-frequency digitized recordings that are continuously recorded chronologically and played back as a video. They are referred to as imaging sonars or acoustic cameras. In contrast to optical systems, multibeam sonar allows for imaging in severe turbidity and complete darkness. The functional principle is based on a transmitter–receiver

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principle of sound or radar waves. They are emitted and their spatial reflection is received and visualized as an image or video. The “viewing” angle of the sound cone of sonars is narrow, and their image resolution is often coarse and partly distorted, but fish movement behaviour of larger fish can be clearly observed under conditions where other methods cannot be applied. Sonar requires substantial manual analysis of the recordings. Objects and structures at distances of up to 10 m can be reliably detected. Under optimal conditions, fish can be observed from a length of about 5 cm (Fig. 4.7). A recommended introduction to the basics of sonar for observing migratory fish is provided by Martignac et al. (2015).

Fig. 4.7 DIDSON image of various fish of a length between 5 and 45 cm (left) and schematic representation of a DIDSON (right) setup for ethohydraulic investigation

Literature

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Future Prospects

The further development of measurement technologies, coupled with numerical flow models make it possible to describe the hydraulic conditions experienced by animals in ethohydraulic experiments more precisely than ever before. In this respect, the fundamental methodical approaches used in today’s ethohydraulic laboratory will not diminish in importance in the future. Ethohydraulic laboratory studies will likely remain the first stage of addressing many of the fundamental questions about the behaviour of aquatic organisms and their reactions and behaviour patterns as they relate to hydraulic engineering installations. In the future, combined behavioural-statistical methods will likely form a key contribution to ensuring the transferability of the findings to the field. Key to transfer is the application of newer measuring techniques and sensors, in particular biologgers, transponders, telemetric transmitters and imaging sonars. Together, they provide promising new information by recording the subjects’ behaviour both in the laboratory and the field. This provides excellent opportunities to validate transfer as the third and final phase of the ethohydraulic method, linking key repeatable findings from laboratory experiments to repeatable observations in the field. The vision and ultimate aim of the ethohydraulics practitioner is to systematically study and improve our understanding of flows and how they shape and guide the fascinating and complex behaviour of aquatic organisms.

Literature Böckmann, I. (2020). Entwicklung eines Verfahrenskataloges für statistisch abgesicherte ethohydraulische Forschungen. In Technische Universität Darmstadt (Hrsg.), Mitteilungen des Instituts für Wasserbau und Wasserwirtschaft, 157. https://doi.org/10.25534/tup rints-00011586 . Boiten, W. (2008). Hydrometry. A comprehensive introduction to the measurement of flow in open channels. CRC Press. Brijs, J., Sandblom, E., Axelsson, M., Sundell, K., Sundh, H., Kiessling, A., Berg, C., & Gräns, A. (2019). Remote physiological monitoring provides unique insights on the cardiovascular performance and stress responses of freely swimming rainbow trout in aquaculture. Scientific Reports, 9(1). Costa, M. J., Fuentes-Pérez, J. F., Boavida, I., Tuhtan, J. A., & Pinheiro, A. N. (2019). Fish under pressure: Examining behavioural responses of Iberian barbel under simulated hydropeaking with instream structures. PLoS ONE, 14(1). https://doi.org/10.1371/jou rnal.pone.0211115 . Deutsche Vereinigung für Wasserwirtschaft, Abwasser und Abfall e. V. (2005). Fischschutzund Fisch-abstiegsanlagen – Bemessung, Gestaltung, Funktionskontrolle. Hennef.

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Deutsche Vereinigung für Wasserwirtschaft, Abwasser und Abfall e. V. (2014). Merkblatt DWA-M 509: Fischaufstiegsanlagen und fischpassierbare Bauwerke – Gestaltung, Bemessung, Qualitätssicherung. Hennef. Franz, V. (1910). Phototaxis und Wanderung nach Versuchen mit Jungfischen und Fischlarven. Hydrobiologia, 3, 306–334. https://doi.org/10.1002/iroh.19100030304 Lucas, M. C., & Baras, E. (2000). Methods for studying spatial behaviour of freshwater fishes in the natural environment. Fish and Fisheries, 1(4), 283–316. Martignac, F., Daroux, A., Bagliniere, J.-L., Ombredane, D., & Guillard, J. (2015). The use of acoustic cameras in shallow waters: New hydroacoustic tools for monitoring migratory fish population. A review of DIDSON technology. Fish and Fisheries, 16, 486–510. Martin, H. (2011). Numerische Strömungssimulation in der Hydrodynamik: Grundlagen und Methoden. Springer. Morgenschweis, G. (2010). Hydrometrie – Theorie und Praxis der Durchflussmessung in offenen Gerinnen. Springer. Schiemenz, F. (1950). Wie soll das Unterende der Fischtreppen in das Hauptwasser einmünden? Versuche mit Glasaalen. Wasserwirtschaft, 40, 130–135. Schiemenz, F. (1952). Versuche mit Glasaalen – Beitrag zur Frage des Hineinleitens wandernder Fische in die untere Mündung einer Fischtreppe. In Technische Hochschule Hannover (Hrsg.). Mitteilungen Der Hannoverschen Versuchsanstalt Für Grundbau Und Wasserbau, 2, 24–33. Schiemenz, F. (1957). Ersatz des instinktmäßigen Wanderns der Fische in Fischtreppen durch das reflektorische Wandern. Z. Fischerei, NF, 6, 61–68. Schmalz, W., Wagner, F., & Sonny, D. (2015). Forum „Fischschutz und Fischabstieg“ – Arbeitshilfe zur standörtlichen Evaluierung des Fischschutzes und Fischabstieges. Im Auftrag des Ecologic Institutes gemeinnützige GmbH. Schwevers, U., & Adam, B. (2020). Fish protection technologies and fish ways for downstream migration. Springer Nature. Steinmann, P. (1913). Über Rheotaxis bei Tieren des fließenden Wassers. Verhandlungen Der Naturforschenden Gesellschaft in Basel, 24, 136–158. Taft, E. P. (1986). Assessment of downstream migrant fish protection technologies for hydroelectric application. Report. In Electrical Power Research Institute (Hrsg.), EPRI Research Project, 2694(1). Tuhtan, J. A., Fuentes-Pérez, J. F., Strokina, N., Toming, G., Musall, M., Noack, M., Kämäräinen, J. K., & Kruusmaa, M. (2016). Design and application of a fish-shaped lateral line probe for flow measurement. Review of Scientific Instruments, 87(045110). https://doi.org/10.1063/1.4946765 . Tuhtan, J. A., Fuentes-Perez, J. F., Angerer, T., & Schletterer, M. (2018a). Monitoring upstream fish passage through a bypass pipe and drop at the fish lift Runserau: Comparing dynamic pressure measurements on live fish with passive electronic fish surrogates. International Symposium on Ecohydraulics 2018a. Tokyo. Tuhtan, J. A., Fuentes-Perez, J. F., Toming, G., Schneider, M., Schwarzenberger, R., Schletterer, M., & Kruusmaa, M. (2018b). Man-made flows from a fish’s perspective: autonomous classification of turbulent fishway flows with field data collected using an artificial lateral line. Bioinspiration & Biomimetics, 13(4). https://doi.org/10.1088/17483190/aabc79

What You Learned From This essential

• Ethohydraulics enables the behavioural study of aquatic animals under set geometric and hydraulic boundary conditions. • The conception of ethohydraulic tests requires a careful, problem-oriented preliminary analysis as well as the construction and operation of a situationally similar test setup with variable boundary conditions. • Ethohydraulic investigations usually take place under conditioned conditions in the laboratory, but can also be carried out in the field if suitable measurement and observation methods are used. • Ethohydraulic investigations use a variety of different methods (e.g. numerical and physical models, telemetry and transponder technologies, different hydraulic and bioinspired measurement technologies) and combine them to a hybrid approach. • The results of ethohydraulic investigations are used for the planning, dimensioning and optimisation of passage and protection facilities for aquatic fauna in and at hydraulic engineering structures - general findings (e.g. hydraulic limit and guideline values), recommendations (e.g. on structure-induced flow signatures) as well as plant-specific functional specifications (e.g. control of a fish lift system or design of a fish protection screen) exist. • New technical developments allow differentiated ethohydraulic investigations, e.g. by the use of autonomous fish probes, fish tracking by telemetry or the collection and evaluation of complex flow data (e.g. turbulence parameters) by hybrid coupling of hydrometric measurements with high-resolution numerical simulations.

© Springer Fachmedien Wiesbaden GmbH, part of Springer Nature 2022 B. Lehmann et al., Ethohydraulics, Springer essentials https://doi.org/10.1007/978-3-658-35416-9

57

Bibliography

Aadland, L. P. (1993). Stream habitat types: their fish assemblages an relation-ship to flow. North American Journal of Fisheries Management, 13, 790–806. Adam, B. (2010). Linear and lateral passage requirements. Fish migration and the importance of floodplain habitats. BfN-Skripten, 280,12–25. Adam, B., & Lehmann, B. (2011). Ethohydraulics—fundamentals, methods, insights. Springer-Verlag. Adam, B., Schwevers, U., & Dumont, U. (1999). Contributions to the protection of migrating fish—behavioural observations in a model channel. Nature & Science. Adam, B., Schürmann, M., & Schwevers, U. (2013). On the management of aquatic organisms. Springer Spectrum. Amaral, S. V., Winchell, F. C., McMahon, B. C., & Dixon, D. A. (2003). Evaluation of an angled bar rack and a louver array for guiding silver American eels to a bypass. American Fisheries Society Symposi-um, 33, 367–376. Ballon, E., & Adam, B. (2016). Development of a mitten crab guidance system for fishways. Water Resources Management, 106(7–8), 36–40. Bates, K. (2000). Fishway guidelines for Washington State (draft guidelines 4/25/00). Washing-ton Department of Fish and Wildlife. Bibliographisches Institut GmbH, 2020—www.duden.de Bleckmann, H., Mogdans, J., Engelmann, J., Kröther, S., & Hanke, W. (2004). The lateral line sys-tem. How fish sense water. Biology in our time, 34(6), 358–365. Böckmann, I. (2020). Development of a procedure catalogue for statistically validated ethohydrological research. In Darmstadt University of Technology (Ed.): Communications of the Institute of Hydraulic Engineering and Water Resources Management, 157. doi: https://doi.org/10.25534/tuprints-00011586. Boiten, W. (2008). Hydrometry. A comprehensive introduction to the measurement of flow in open channels. CRC Press. Bone, Q., & Marshall, N. B. (1985). Biology of fishes. Gustav Fischer. Brijs, J., Sandblom, E., Axelsson, M., Sundell, K., Sundh, H., Kiessling, A., Berg, C., & Gräns, A. (2019). Remote physiological monitoring provides unique insights on the cardiovascular performance and stress responses of freely swimming rainbow trout in aquaculture. Scientific Reports, 9(1). Coarer, Y. L. (2007). Hydraulic signatures for ecological modeling at different scales. Aquatic Ecolo-gy, 41, 451–459. © Springer Fachmedien Wiesbaden GmbH, part of Springer Nature 2022 B. Lehmann et al., Ethohydraulics, Springer essentials https://doi.org/10.1007/978-3-658-35416-9

59

60

Bibliography

Costa, M. J., Fuentes-Pérez, J. F., Boavida, I., Tuhtan, J. A., & Pinheiro, A. N. (2019). Fish under pres-sure: Examining behavioural responses of Iberian barbel under simulated hydropeaking with in-stream structures. PLoS ONE, 14(1). doi: https://doi.org/10.1371/ journal.pone.0211115 Deutsche Vereinigung für Wasserwirtschaft, Abwasser und Abfall e.V.. (2005). Fish protection and descent systems—dimensioning, design, functional control. Hennef. Deutsche Vereinigung für Wasserwirtschaft, Abwasser und Abfall e.V.. (2014). Code of Practice DWA-M 509: Fishways and fish-passable structures - design, dimensioning, quality assurance. Hennef. Ebel, G. (2013). Fish protection and fish bypass at hydropower plants. Manual of rake and by-pass systems. self-published. Electrical Power Research Institute (2016). Laboratory Studies of eel behavior in response to various behavioral cues. Technical Report. Palo Alto. Engler, O., & Adam, B. (2020). Influence of light conditions on fishway efficiency. Species Conservation Report, 41, 41–47. European Parliament and Council of the European Union (2000). Directive 2000/60/EC of the European Parliament and of the Council of the European Union of 23. 10. 200 establishing a framework for Community action in the field of water policy. Official Journal of the European Communities L 327/1–327/72 of 22.12.2000. Fladung, E. (2000). Studies on stock regulation and exploitation of the Chinese mitten crab (Eriocheir sinensis). Schriften des Instituts für Binnenfischerei Potsdam-Sacrow, 5. Flügel, D., Bös, T., & Peter, A. (2015). Research project: Measures to ensure gentle fish descent at larger Central European river power plants. EAWAG. Franz, V. (1910). Phototaxis and migration after experiments with juvenile fish and fish larvae. Hyd-robiologia, 3, 306–334. doi: https://doi.org/10.1002/iroh.19100030304. Gerhardt, P. (1912). The fishways. In Handbuch der Ingenieurwissenschaften, 3. part, II. vol., 1. dept. weirs and fishways (pp. 454–499). Gosset, C., & Travade, F.. (1999). Devices to aid downstream salmonid migration: behavioural barri-ers. International Journal of Ichthyology, 23(1), 45–66. Gough, P., Philipsen, P., Schollema, P. P., & Wanningen, H. (2012). From sea to source: International guidance for the restoration of fish migration highways, Regional Water Authority Hunze en Aas. Hadderingh, R. H., van Aerssen, G. H. F. M., de Beijer, R. F. L. J., & van der Velde, B. (1999). Reaction of silver eels to artificial light sources and water currents: an experimental deflection study. Regulated Rivers: Research & Management, 15,365–371. Hoar, W. S., & Randall, D. J. (1978). Fish Physiology, Volume VII “Locomotion.” Academic Press. Hut, M. (2000). Ecology and hydraulic engineering—Ecological foundations of river engineering and hydropower use. Parey. Larinier, M., & Boyer-Bernard, S. (1991a). Dévalaison des smolts et efficacité d’un exutoire de déva-laison à l’usine hydroélectrique d’Halsou sur la Nive. Bulletin Français de la Pêche Pisciculture, 321, 72–92. doi: https://doi.org/10.1051/kmae:1991a009. Larinier, M., & Boyer-Bernard, S. (1991b). La dévalaison des smolts de saumon Atlantique au bar-rage de Poutès sur l’Allier (43): utilization de lampes a vapeur de mercure. Bulletin Français de la Pêche Pisciculture, 323, 129–148. doi: https://doi.org/10.1051/kmae:199 1b001.

Bibliography

61

Larinier, M., Travade, F., & Porcher, J. P. (2002). Fishways: biological basis, design criteria and moni-toring. Bulletin Français de la Pêche et de la Pisciculture, 354. Lehmann, B., Adam, B., Engler, O., & Schneider, K. (2016). Ethohydraulic studies to improve fish protection at hydropower plants. In Federal Agency for Nature Conservation (Ed.), Nature Conservation and Biodiversity, 151. Liao, J. C. (2007). A review of fish swimming mechanics and behaviour in altered flows. Philosophical Transactions of The Royal Society B Biological Sciences, 362, 1973–1993. Lowe, R. H. (1952). The influence of light and other factors on the seaward migration of silver eel. Journal of Animal Ecology, 21(2), 275–309. Lucas, M. C., & Baras, E. (2000). Methods for studying spatial behaviour of freshwater fishes in the natural environment. Fish and Fisheries, 1(4), 283–316. Lucas, M. C., & Baras, E. (2001). Migration of freshwater fishes. Blackwell Science. Lupandin, A. I. (2005). Effect of flow turbulence on swimming speed of fish. Biology Bulletin, 32(5), 461–466. Martignac, F., Daroux, A., Bagliniere, J.-L., Ombredane, D., & Guillard, J. (2015). The use of acoustic cameras in shallow waters: new hydroacoustic tools for monitoring migratory fish population. A review of DIDSON technology. Fish and Fisheries, 16, 486–510. Martin, H. (2011). Numerical flow simulation in hydrodynamics: Fundamentals and metho-ds. Springer. Meyer-Waarden, P. F. (1954). Electric barriers for the control of mitten crabs. Der Fischwirt, 4, 331–337, 357–364. Ministry for the Environment and Nature Conservation, Agriculture and Consumer Protection of the State of North Rhine-Westphalia (2005). Handbook of transverse structures. Klenkes. Morgenschweis, G. (2010). Hydrometry—theory and practice of flow measurement in open channels. Springer. Panning, A. (1938). On the migrations of the mitten crab. Marking experiments. New investigations on the Chinese mitten crab in Europe. In Zoologisches Intitut und Zoologi-sches Museum Hamburg (eds.), Mitteilungen aus dem Hamburgischen Zoologischen Museum und Institut, 47, 32–49. Schiemenz, F. (1950). How should the lower end of fish ladders enter the main water? Experiments with glass eels. Water Management, 40, 130–135. Schiemenz, F. (1952). Experiments with glass eels - Contribution to the question of the introduction of migrating fish into the lower mouth of a fish ladder. In Technische Hochschule Hannover (ed.), Mit-teilungen der Hannoverschen Versuchsanstalt für Grundbau und Wasserbau, 2, 24–33. Schiemenz, F. (1957). Replacement of instinctive migration of fish in fish ladders by reflex migration. Z. Fischerei, NF 6, 61–68. Schiemenz, F., & Koethke, H.. (1935). On the mitten crab and suggestions for its mass catch. Mitteilungen der Fischerei-Ver. Ostausgabe, 24(2/3), 25–32, 45–56. Schmalz, W., Wagner, F., & Sonny, D. (2015). Forum “Fish Protection and Fish Descent”— Working aid for site-specific evaluation of fish protection and fish descent. Commissioned by Ecologic Institute gemeinnützige GmbH. Schwevers, U., & Adam, B. (2020). Fish Protection Technologies and Ways for Downstream Migra-tion. Springer Nature Switzerland.

62

Bibliography

Schwevers, U., Schindehütte, K., Adam, B., & Steinberg, L. (2004). Investigations on the passability of culverts for fish. In Landesanstalt für Ökologie, Bodenordnung und Forsten Nord-rhein-Westfalen (Ed.), LÖBF-Mitteilungen, 28(3), 37–43. Sellheim, P. (1996). Crossing structures in flowing waters - design proposals for culverts, bridges, piping and culverts. Information Service Nature Conservation Lower Saxony, 16, 205–208. Silva, A. T., Lucas, M. C., Castro-Santos, T., Katopodis, C., Baumgaertner, L. J., Thiem, J. D., Aarest-rup, K., Pompeu, P. S., O’Brien, G. C., Braun, D. C., Burnett, N. J., Zhu, D. Z., Fjeldstad, H.-P., For-seth, T., Rajaratnam, N., Williams, J. G., & Cooke, S. J. (2018). The future of fish passage science, engineering, and practice. Fish and Fisheries, 19(2), 340–362. Statzner, B., Gore, J. A., & Resh, V. H. (1988). Hydraulic stream ecology: observed patterns and po-tential applications. Journal of the North American Benthological Society, 7(4), 307–360. Steinmann, P. (1913). On rheotaxis in animals of flowing water. Verhandlungen der Naturforschenden Gesellschaft in Basel, 24 (pp. 136–158). Taft, E. P. (1986). Assessment of downstream migrant fish protection technologies for hydroelectric application. Report. In Electrical Power Research Institute (ed.), EPRI Research Project, 2694(1). Tuhtan, J. A., Fuentes-Pérez, J. F., Strokina, N., Toming, G., Musall, M., Noack, M., Kämäräinen, J. K., & Kruusmaa, M. (2016). Design and application of a fish-shaped lateral line probe for flow meas-urement. Review of Scientific Instruments, 87(045110). doi: https://doi.org/10.1063/1.4946765. Tuhtan, J. A., Fuentes-Perez, J. F., Angerer, T., & Schletterer, M. (2018a). Monitoring upstream fish passage through a bypass pipe and drop at the fish lift Runserau: Comparing dynamic pressure measurements on live fish with passive electronic fish surrogates. International Symposium on Ecohydraulics. Tuhtan, J. A., Fuentes-Perez, J. F., Toming, G., Schneider, M., Schwarzenberger, R., Schletterer, M., & Kruusmaa, M. (2018b). Man-made flows from a fish’s perspective: autonomous classification of turbulent fishway flows with field data collected using an artificial lateral line. Bioinspiration & Bio-mimetics, 13(4). doi: https://doi.org/10.1088/ 1748-3190/aabc79. Vordermeier, T., & Bohl, E. (2000). Fish-friendly design of transverse and longitudinal structures in small streams. In Landesfischereiverband Bayern (Ed.), Schriftenreihe des Landesfische-reiverbands Bayern, 2 (pp. 53–61).