As Ethohydraulik an engineering biological field is called, the interdisciplinary intersection of ethology (Greek .: study of animal behavior) and hydraulic (Greek .: doctrine of the motion of fluids, see Fluid Mechanics and hydromorphology ) was created. The aim of this discipline is to derive guidelines for a more ecologically compatible hydraulic engineering practice on the basis of research and understanding of the needs of aquatic fauna , especially fish.
In 2000, the European Parliament of the European Community enacted the European Water Framework Directive , which was accompanied by a paradigm shift for the orientation of water management activities: Whereas previously compliance with chemical / physical quality values in still and flowing waters was decisive, in future it will also apply to the ecological status of surface waters to protect or improve. The evaluation basis for this is the characteristics of the aquatic communities . Current surveys, however, show massive population deficits, so that the specified goal of a good ecological status will probably not be achieved in many catchment areas.
The cause of this situation are anthropogenic demands on the use of water, which are expressed in various hydraulic engineering measures and structures. B. for shipping, energy generation, flood protection, drinking water production, sport and leisure use, etc. What all these hydraulic engineering activities have in common is that in the past they were carried out largely without considering the needs of aquatic organisms. So the continuity of flowing water systems is for upstream migrating organisms by numerous storage buildings interrupted, by hydroelectric power plants damaged and pumps downstream migrating fish to a considerable extent and meet many restoration measures Although landscape aesthetic, but not meeting the needs of plants and animals. Even fish ladders often only insufficiently fulfill their original purpose, as the requirements of the fish on such structures are insufficiently known or have not been adequately taken into account in planning and construction.
A major reason for the sparse knowledge about the requirements of the fish fauna in particular is that these very mobile organisms evade direct observation under natural conditions. That is why studies of the behavior of fish in water are very time-consuming and labor-intensive.
On the other hand, the various factors that influence the behavior of fish are subject to permanent fluctuations, making them difficult to measure and interpret with regard to their ecological significance. In addition, since the benefits of such basic research have so far been misunderstood, there are virtually no fish-ecologically relevant criteria or parameters with regard to a targeted ecological upgrading of water bodies for hydraulic engineering practice.
Against this background, the interdisciplinary ethohydraulics was developed at the Institute for Water and Water Development at the University of Karlsruhe in collaboration with biologists from the Institute for Applied Ecology from 2007 to 2009. This research and development project was funded by the German Federal Environment Foundation (DBU).
The procedure and its methodological requirements
Ethohydraulic investigations are only useful if both the technical work, such as the planning of the test stand and hydraulic measurements, as well as the behavioral observations are carried out in a team of hydraulic engineers and biologists. Other features are that large-scale test stands are required and that each project runs in three phases.
Phase 1: Preprocessing (analysis of the hydraulic natural situation and modeling of this in the laboratory)
In most cases it is not possible to reproduce all the geometric and hydraulic conditions of a natural situation in the hydraulic engineering laboratory. When planning ethohydraulic tests, it must therefore be ensured that a laboratory channel is equipped and controlled in such a way that the fish used in it are confronted with a situation similar to that in water. That is why the behavior is primarily influenced by parameters, e.g. B. to realize flow velocity and turbulence on a scale of 1: 1, while taking into account the morphology of the fish, the scale may be changed, especially geometric parameters.
Due to infrastructural restrictions, it is not always possible to simulate all primary parameters at the same time. It is conceivable that it is not possible to simulate real flow velocities at real water depths at the same time. In such cases, separate test series are required in which, on the one hand, varying flow velocities are used at constant water depth and, on the other hand, varying water depths while the flow velocity remains constant.
Phase 2: Processing (live animal observation and recording of the hydraulic signature)
Live animal observations with vertebrates are subject to the Animal Welfare Act . Just like keeping fish for scientific purposes, ethohydraulic tests are generally subject to approval and are reserved for authorized specialist staff.
If these prerequisites are fulfilled, the behavior of the fish is observed under conditioned conditions in order to identify those reactions from the entire behavior repertoire with which the fish responds to the given hydraulic situation. In order to be able to recognize parameter-specific reactions of fish at all, a comparative approach is generally used in which only one parameter is changed in successive tests and an impact on the behavior of the fish is sought.
If the ethohydraulic tests result in reproducible behavior, which is to be understood as a reaction to a certain parameter or a parameter constellation, the factors relevant to the fish must be measured, e.g. B. geometries, flow speeds and directions, flow impulses, turbulence or turbulent kinetic energies .
Phase 3: Postprocessing (implementation of the findings in hydraulic engineering practice)
Knowledge of the hydraulic criteria and signatures from ethohydraulic tests ultimately enables the scientifically founded derivation of fish-relevant requirements, rules and parameters. These are to be incorporated into hydraulic engineering practice as concrete planning and dimensioning specifications, thereby contributing to the implementation of hydraulic engineering measures in a more compatible manner and to erecting and operating structures and systems in accordance with ecological requirements.
Live animal observations with fish are repeatedly carried out in hydraulic engineering laboratories all over the world, although these often differ fundamentally in terms of their practical relevance, methodological approach and the type of analysis and interpretation. Accordingly, the findings are often rather anecdotal because they are not very reliable, cannot be reproduced or are contradictory. Nevertheless, many findings from these few ethohydraulic studies became part of the international state of knowledge and technology and found their way into national regulations. The following examples are intended to illustrate the utility of ethohydraulic research:
Example 1: Effect of mechanical barriers to protect migrating fish
The fishing laws of most federal states require the installation of rakes with a maximum clear width of 20 mm in front of the inlets of engines and water extraction systems in order to protect migrating fish against penetration into hydraulic structures that endanger them . Ethohydraulic tests with such rakes revealed that even eels up to a body length of 70 cm can pass such 20 mm rakes (Figure 1a). In addition, many fish are inescapably pressed against the rake surfaces at an inflow speed of only 0.5 m / s until they die as a result of injuries or exhaustion (Figure 1b). For comparison: water power plants are usually approached at speeds of over 1 m / s. These findings make it necessary to reduce the clear width of rakes to protect eels to a maximum of 15 mm and at the same time to limit the flow velocity to a maximum of 0.5 m / s.
Example 2: Substrate preference of poorly performing fish
It is generally accepted that underperforming fish seek protection from the current on the leeward side of the roughness of the bottom. This postulated need for various small fish species and young stages of development to retreat into a quiet zone known as “flow shadow” was examined with the aid of a laboratory channel covered in sections with different surface roughness. It was found that underperforming fish (e.g. small bream and roach ) avoid the leeward side of roughness elements at medium flow speeds of 0.4 m / s in order to evade vortex streets that detach at the contour edges ( Figure 2a). In contrast, they are concentrated in sections with a few roughness elements of a maximum height of 15 cm (Figure 2b). From these findings the need arises, for. B. to limit the roughness of the bottom of passages and in fish ladders with consideration of the needs of underperforming species.
- EU (2000): Directive 2000/60 / EC of the European Parliament and of the Council of October 23, 2000 on the creation of a framework for Community measures in the field of water policy. - Official Journal of the European Communities L 327/1 - 327/72 of 22 December 2000.
- KREITMANN, L. (1931): Contribution à l'étude des characteristiques des passes à poissons: la vitesse de nage des poissons. - Relationship international association. Limnol. 5, 345-353.
- PAVLOV, DS, YN SBIKIN, AY VASHEHINNIKOX & AD MOCHEK (1972): The effect of light intensity and water temperature on the current velocities critical to fish. - J. Ichthyol. 12, 703-711.
- ADAM, B. & U. SCHWEVERS (1997): The behavior of fish in fish ladders. - Austrian Fisheries 50, 82-87.
- ADAM, B. & U. SCHWEVERS (1998): On the findability of fish ladders - behavioral observations on fish in a model channel. - Water & Soil 50/4, 55 - 58.
- HASELBAUER, MA & C. BARREIRA MERTINEZ (2007): Proposal of a Sluicetype Fish Pass. - Neotropical Ichthyology 5 (2), 223-228.
- AMARAL, SV, FC WINCHELL, BJ MCMAHON & DA DIXON (2000): Evaluation of an angled bar rack and a louver array for guiding silver American eels to a bypass. - 1st International Catadromous Eel Symposium, St. Louis / Missouri, 20.-24. August 2000, Symposium Pre-Prints, 8 pp.
- ADAM, B., U. SCHWEVERS & U. DUMONT (1999): Contributions to the protection of migrating fish - behavioral observations in a model channel. - Solingen (Verlag Natur & Wissenschaft), Library Nature and Science 16, 63 pp.
- DVWK (1996): Leaflets on water management 232/1996: Fish passages - dimensioning, design, function control. Ed .: DVWK (German Association for Water Management and Cultural Building eV) - Bonn (Wirtschafts- und Verlagsgesellschaft Gas und Wasser mbH), 110 pp.
- DWA (2005): Fish protection and fish descent systems - dimensioning, design, functional control. - Hennef (DWA - German Association for Water Management, Sewage and Waste eV), 2nd corrected edition, 356 pp.
- DWA (2009): Natural sole gliding. - DWA topic volume, Hennef, 142 pp.
- ADAM, B., W. KAMPKE, O. ENGLER & C. LINDEMANN (2009): Ethohydraulic tests on the roughness preference of small fish species and individuals - special report for the DBU project "Ethohydraulics - a basis for water engineering compatible with nature conservation" (project number 25429-33 / 2), 32 pp.