What do we know to evaluate the health of brown trout (Salmo trutta) populations?

in Proceedings of the 9th International Conference on Ecohydraulics (2012, September)

The renewed emphasis on the concept of the health of ecosystems highlights society’s interest in taking measures to protect environments transformed by human activity. The criteria used for evaluating the ... [more ▼]

The renewed emphasis on the concept of the health of ecosystems highlights society’s interest in taking measures to protect environments transformed by human activity. The criteria used for evaluating the health of fish population are rarely discussed within the scientific community. The exercise proposed here aimed to discuss these for the brown trout (Salmo trutta), a flagship species from the freshwater fish community typical from headwaters of watercourses which represent most of the French hydrographic network. This initiative aimed to gather the ideas of a limited number of experts on the function of these populations and on the criteria for evaluating their function. The main key parameters were identified and organised into a hierarchical framework for each development stage. A consensus emerged on the fact that in the current stage of knowledge, the diagnosis can be established based on the analysis of abiotic parameters crucial for the biology and, with more difficulty, on the analysis of biotic parameters. For all the development stages, the identified parameters are linked to habitat (substrate, stream flow, temperature and water quality), hydrology and connectivity. Further knowledge must be acquired in order to be able to measure the biological criteria. That implies to reinforce longterm biological monitoring and research to understand the variability in biological parameters, the relevant spatiotemporal scales and the functional processes. [less ▲]

Probability of detection and positioning error of a hydro acoustic telemetry system in a fast-flowing river: intrinsic and environmental determinants

in Fisheries Research (2012), 125-126

In situ fixed acoustic telemetry methods make it possible to study simultaneously the detailed movements of individual fish and their relationship to the environment, but the properties of these methods ... [more ▼]

In situ fixed acoustic telemetry methods make it possible to study simultaneously the detailed movements of individual fish and their relationship to the environment, but the properties of these methods is little known in harsh physical conditions. We examined the probability of tag detection by the system and the positioning error for detected tags of an existing telemetry system installed with 32 fixed hydrophones in a reach of the fast-flowing Rhône River in France. The reach was 1.8 km long and had heterogeneous thermal and hydraulic conditions described by a two-dimensional hydraulic model. We compared positions detected by the system with true positions estimated using a tachometer or a differential GPS, for various sets of experimental tag emissions. We analyzed how the probability of detection and the positioning error were affected by user-defined variables and three groups of environmental variables describing the configuration of the hydrophones around tag position, the physical environment at tag position and the reception quality. Tag emissions from the center channel had an average probability of detection (40-50%) higher than emissions originating from positions close to the banks, and were positioned with smaller average errors (3-5 m). The probability of detection of emissions typically varied between near 0% and 80% with configuration variables (density of surrounding hydrophones and location of tag relative to the hydrophones) and also decreased in the presence of coarse substrate. The positioning error was mainly reduced when user-defined variables of the triangulation software were set by an expert user. Configuration variables also influenced the positioning error with weaker effects than those observed for detection probability. [less ▲]

Use of Fixed and Mobile Acoustic Telemetry Systems to Understand Fish Responses to Habitat Variability in a Large River (Rhône, France)

Conference (2011, September)

The presentation would summarize the advantages and limitations of both fixed and mobile acoustic telemetry equipment deployed in a fast flowing large river : the Rhône river (France). The objectives were ... [more ▼]

The presentation would summarize the advantages and limitations of both fixed and mobile acoustic telemetry equipment deployed in a fast flowing large river : the Rhône river (France). The objectives were to describe fish behavior in term of fish movements as responses to habitat variability due to the production of peaking electricity and temperature heterogeneity (natural or due to a nuclear power plant release). At a local scale we used a fixed automatic acoustic telemetry system to record continuous movements of n=62 fish during short term (lower than day) habitat variability. The study was conducted in a 2 km long river stretch, from July to September 2009. In a 35 km long study site, we used a mobile acoustic telemetry system to record weekly position of n=108 fish over different seasons and different habitat conditions (low or high flows; low or high temperature...), from March to December 2010. Discharge and abiotic conditions (temperature, depth, velocity or substrate) were known (with an accuracy comparable with fish positioning accuracy) every where at any time (i.e. any discharge) using hydraulic 2D model calibrated and validated for the whole discharge range observed during telemetry studies. Fixed telemetry system (accuracy of few square meters) enabled to define individual habitat use during different short habitat variability configuration (flow increase, flow decrease, temperature increase....). Three main species were represented : two native cyprinids, chub (Leuciscus cephalus) and barbel (Barbus barbus), and an invasive species, wels catfish (Silurus glanis). We analyzed habitat used, habitat preference, fish movement patterns versus habitat variability. Mobile telemetry system (accuracy of few hundred square meters) enabled to evaluate space and time utilisation of fish (mainly the same species than for fixed telemetry study) at a larger scale and during different seasons encompassing the reproduction period, the summer or the winter periods. The different results obtained by both telemetry systems will be presented to illustrate the advantages and limitations of those systems in a large river to address fish displacement in response to discharge and temperature variability. This comparison also emphasized the contribution of a 2D hydrodynamic model to understand fish behaviour. [less ▲]

Regulated discharge produces substantial demographic changes on four typical fish species of a small salmonid stream

in Hydrobiologia (2008), 609

A hydroelectric power plant (HPP) started operation in December 2002 on the River Lhomme, (mean annual flow: 1.78 m(3) s(-1)supercript stop; mean annual water temperature: 9.9 degrees C). The new HPP ... [more ▼]

A hydroelectric power plant (HPP) started operation in December 2002 on the River Lhomme, (mean annual flow: 1.78 m(3) s(-1)supercript stop; mean annual water temperature: 9.9 degrees C). The new HPP bypasses the river over a length of 1.2 km. The minimum flow allowed in the bypassed section is currently fixed at 0.220 m(3) s(-1)supercript stop. Before the construction of the HPP, two contrasted 150-m-long reaches of the Lhomme were selected to estimate their total fish population abundance and to analyse their fish population dynamics. Electrofishing was carried out in each of these two reaches on 23 April 2002 in a natural flow situation to remove the fish. Other inventories were carried out in late April or early May in 2003, 2004, 2005 and 2006 in minimum flow conditions. The results revealed a prompt and severe decrease in the total fish biomass (up to 81% for grayling from 2002 to 2006) combined with severe changes in the fish community structure that were not observed in a reference site. The effects of the flow reduction varied considerably depending on the size of the individuals, the species concerned and their habitat availability, which was modelled using a classical physical habitat simulation (EVHA method). [less ▲]

Field protocol for assessing small obstacles to migration of brown trout Salmo trutta, and European grayling Thymallus thymallus: a contribution to the management of free movement in rivers

in Fisheries Management and Ecology (2007), 14(1), 41-50

Between 1996 and 2004, adult brown trout, Salmo trutta L. (n = 40) and European grayling, Thymallus thymallus (L.) (n = 39) were radio-tracked in three southern Belgium rivers to assess their capabilities ... [more ▼]

Between 1996 and 2004, adult brown trout, Salmo trutta L. (n = 40) and European grayling, Thymallus thymallus (L.) (n = 39) were radio-tracked in three southern Belgium rivers to assess their capabilities to bypass various obstacles. During their upstream migrations individuals encountered different types of physical obstacles and successfully passed some under variable environmental conditions. The obstacles cleared by the fish were characterised based on a simple topographical description protocol and compared with tracking data. The ability of trout and grayling to pass different typologies of physical obstacles in natural river systems is discussed in the context of enabling their free movement in rivers. [less ▲]

Impacts de la mise en service d'une microcentrale hydroélectrique sur les populations de poissons de la Lhomme à Poix Saint-Hubert

Report (2006)

Ce rapport présente une partie des résultats des recherches menées dans le cadre d’une convention d’études 2005-2007 entre le Ministère de la Région Wallonne (Division de l’Eau, Direction des Cours d’Eau ... [more ▼]

Ce rapport présente une partie des résultats des recherches menées dans le cadre d’une convention d’études 2005-2007 entre le Ministère de la Région Wallonne (Division de l’Eau, Direction des Cours d’Eau Non Navigables) et l’Université de Liège (Laboratoire de Démographie des Poissons et d’Hydroécologie, Unité de Biologie du Comportement). L’objet particulier de la recherche évoquée est le suivi biologique de la population piscicole de la Lhomme à Poix Saint-Hubert après la construction et la mise en service en fin 2002 d’une microcentrale hydroélectrique par la société S.A. Hydroval. La réalisation de cette étude correspond à une étude d’impact a posteriori, dont la réalisation conditionnait l’octroi du permis d’exploitation. Cette recherche très ciblée est une composante d’une convention d’études générale intitulée « Définition de bases biologiques et éco-hydrauliques pour la libre circulation des poissons dans les cours d'eau non navigables de Wallonie ». [less ▲]