Bioseguridad dentro del Hato

The scientific evidence for a cause-effect relationship between flow variability and a specific fish response was scarce before the materialization of this research. Most studies addressed changes in fish assemblages in their natural habitat. Hence, it was challenging to find such causality. To identify that mechanistic link it is necessary to level down to lower ecological units, specifically to the organism-level. The first general objective of this research, corresponding to the first part of the thesis, was to provide

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the scientific community a comprehensive overview of the existing evidence for organism-level responses of fluvial fish to flow variability. The gathered insight provided knowledge to select potential fish responses as biomarkers for flow variability for future research in both natural and modified flow conditions. For the purpose of this thesis, this review was the starting point for the experimental research to be conducted, particularly regarding the choice of physiological responses to rapid flow fluctuations.

To date, the conceptualization of habitat mitigation measures to hydropeaking consequences for cyprinids and their implementation in natural conditions is practically inexistent. To address the causality between flow variability and a specific fish response, and to minimize the effects of confounding variables that naturally occur in the river ecosystem, the rapid flow fluctuations associated to hydropeaking were simulated in an indoor flume located at the Laboratory of Hydraulics at IST, University of Lisbon. In this sense, the general objective of the second part of this thesis was to quantify the behavioural responses of L. bocagei, to simulated hydropeaking, and to conceptualize refuges as a morphological mitigation measure. A multidisciplinary approach was adopted, which included the quantification of physiological responses and movement behaviour frequency, hydraulic modelling, and fluid-body interactions. The specific objectives of this thesis (first and second part) were to:

 Review the existence and utility of organism-level responses that may be used as biomarkers to assess the effects of flow variability in fluvial fish;

 Examine the effects of simulated base-flow and hydropeaking conditions on the physiology and movement behaviour of L. bocagei at an indoor flume equipped with artificial structures as potential velocity refuges;

 Conceptualize alternative structures and spatial arrangements as mitigation measures to hydropeaking consequences for L. bocagei;

 Analyse whether L. bocagei use the available structures equally under simulated base-flow and hydropeaking conditions;

 Analyse the swimming behaviour of L. bocagei under simulated hydropeaking conditions in the presence or absence of structures;

 Identify the hydropeaking conditions that have the lowest and the strongest effects in L. bocagei, based on the physiological and behavioural responses together with the characterization of the hydrodynamic conditions;

 Find critical thresholds of local hydrodynamic variables for L. bocagei, according to the physiological and behavioural responses;

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1.9 Methodological approach

For the first part of this research a systematic bibliographic review was conducted. A search string, consisting of relevant keywords in the topic of flow variability as an organism-level stressor for fluvial fish, was inserted in the Thomson and Reuters Web of Science database. To identify such relationship, a comprehensive analysis of the literature was conducted. The literature that was analysed included natural and anthropogenic flow variability, and in situ and laboratory studies. The organism- level responses considered for the analyses were the primary, secondary and tertiary-level responses.

For the second part of this research, the classical scientific method that characterizes natural sciences was used. Starting with the hydropeaking problematic and following with the formulation of the hypotheses, the research consisted of systematic observations, measurements, formulation of new hypotheses and new measurements, thus depicting a full experimental structure.

The experiments were conducted at the indoor flume which intended to mimic a river reach. Under these conditions, it was possible to control the flow changes, and to isolate the effect of potential confounding variables. The indoor flume has a false bottom where it was possible to install different structures that were conceptualized as potential refuges. The effects of hydropeaking were firstly studied in the presence of lateral deflectors, which are broadly used in restoration actions (Pretty et al., 2003) (see 3.1.3 and 3.2.4). As new questions emerged, instream structures were conceptualized in the last experiment (see 4.1.3). A diverse set of flow events was tested, where magnitude, peak duration, peak frequency and event duration changed. For all experiments, the base-flow conditions consisted of a continuous 7 l.s-1 _{flow event. The peak discharges tested were 20, 40 and 60 l.s} -1_{. The choice of these} discharges changed in the progress of the experiments.

To examine the effects of hydropeaking and the presence or absence of structures for L. bocagei, a novel and multidisciplinary methodological approach was used. It combined fish responses at the organism-level and whole-animal performance, with a detailed characterization of the hydraulic and hydrodynamic conditions created in the flume. To find out whether the rapid flow changes presented a stressor for L. bocagei, blood glucose and lactate were selected as secondary level responses of the HPI axis. Whole animal performance was analysed by quantifying specific movement behaviour metrics related with the flow events and the refuges tested. In this sense, refuge use and swimming activity metrics likely to be visible under hydropeaking conditions were quantified. To characterize the hydraulic conditions and the hydrodynamic environment two technological approaches were used: (i) point velocity measurements using ADV, followed by a calibration to a theoretical 3D hydrodynamic model (see 3.1.3 and 3.2.4), and (ii) a novel technology, the LLP, which measures fluid-body interactions (see 4.1.3).

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With the findings from this multidisciplinary approach it was possible to propose operational alternatives and morphological measures to mitigate the effects of hydropeaking for L. bocagei. Hopefully these may be the basis for future research and followed by hydropower plant managers.