Publications of Arnaud Dierckx
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See detailEvaluation de la qualite biologique des rivieres Wallonnes sur base des indices biologiques poissons. Support technique aux inventaires 2020
Dierckx, Arnaud ULiege; Benitez, Jean-Philippe ULiege; Renardy, Séverine ULiege et al

Report (2020)

Ce document reprend les informations recueillies dans le cadre d’un travail effectué par l’Université de Liège pour le compte du Service public de Wallonie-DEMNA et financé dans le cadre d’un marché ... [more ▼]

Ce document reprend les informations recueillies dans le cadre d’un travail effectué par l’Université de Liège pour le compte du Service public de Wallonie-DEMNA et financé dans le cadre d’un marché public de services qui a pour objectif l’évaluation de la qualité biologique des eaux de surface basée sur les indices biologiques « poissons » dans huit cours d’eau de Wallonie. Cette mission s’inscrit dans le contexte de la mise en oeuvre de la Directive cadre 2000/60/CE établissant un cadre pour une politique communautaire dans le domaine de l’eau. Ce rapport présente les résultats des inventaires piscicoles effectués en mai, juin et juillet 2020 [less ▲]

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See detailSuivi de la dévalaison dans la Vesdre et mesure du fonctionnement des ouvrages pour la faune piscicole
Benitez, Jean-Philippe ULiege; Renardy, Séverine ULiege; Dierckx, Arnaud ULiege et al

Report (2020)

Ce rapport présente les résultats des recherches menées dans le cadre du marché public de Service N°O3.06.04-19D014 : « Suivi de la dévalaison dans la Vesdre et mesure du fonctionnement des ouvrages pour ... [more ▼]

Ce rapport présente les résultats des recherches menées dans le cadre du marché public de Service N°O3.06.04-19D014 : « Suivi de la dévalaison dans la Vesdre et mesure du fonctionnement des ouvrages pour la faune piscicole », publié par le Service Public de Wallonie –Direction Générale Agriculture, Ressources naturelles et Environnement – DDRCB - Direction des Cours d’Eau Non Navigables (Ir Olivier Detrait). Ce projet a été obtenu par le bureau d’étude PROFISH en sous-traitance avec l’Université de Liège – Laboratoire de Démographie des poissons et d’Hydroécologie. Cette étude a pour objectif de déterminer les capacités de dévalaison des poissons sur un cours d’eau de première catégorie et confrontés à différents barrages et centrales hydroélectriques. Le modèle biologique étudié pour cette étude est le smolt de saumon atlantique, Salmo salar, (migration de dévalaison printanière) et le cours d’eau choisi est la Vesdre, rivière fragmentée par de nombreux barrages, dont le barrage de Bacquelaine, équipé d’une Vis d’Archimède. Plus précisément, cette étude vise à déterminer des taux de franchissement et des voies de passages au droit d’ouvrages hydroélectriques ainsi que des timings de migration afin d’évaluer l’incidence des ouvrages cumulés sur la bonne progression de la dévalaison des smolts. [less ▲]

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See detailEvaluation of the performance of successive multispecies improved fishways to reconnect a rehabilitated river
Ovidio, Michaël ULiege; Sonny, Damien; Watthez, Quentin et al

in Wetlands Ecology and Management (2020), 28

The equipping of barriers with fishways has useful applications for testing hypotheses of fish migration and connectivity in river networks, but multiple passage performance for potamodromous fish is ... [more ▼]

The equipping of barriers with fishways has useful applications for testing hypotheses of fish migration and connectivity in river networks, but multiple passage performance for potamodromous fish is poorly known to date. The aim of this study was to analyse the performance of new fishways installed in the river Vesdre (Belgium). Thirty-eight barbel (Barbus barbus; mean: 508 mm, 2133 g) and seven chub (Squalius cephalus; mean: 372 mm, 935 g) were captured by electric fishing and fish pass monitoring and were equipped by RFID-tags and/or radio-transmitters. They were translocated downstream of three different fishways (nature-like pool-type, block ramp, and technical pool-type) in the lower course of the Vesdre. Detection antennas connected to automatic receivers were placed downstream and upstream of each fishway to evaluate the approaching rate, the overall and adjusted passage efficiencies, the passage delays, temperature, dates and time period. The best passage performance and passage delays were observed for the block ramp fishway (88%; 9 h median time to pass) in comparison with pool structures (47 and 73%; 94 and 144 h median time to pass, respectively). The overall passage efficiency was 18.2 and 29.4% for two successive fishways, and 18.2% for three fishways. Passages occurred mainly during dark periods at median temperatures of 14 C (barbel) and 12.3 C (chub), and during highly variable flow conditions. This study provided evidence of the success rate of the reestablishment of the ecological continuity in the river Vesdre as a result of the construction of improved fish-passage structures. [less ▲]

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See detailDevelopment of an accurate model to predict the phenology of Atlantic salmon smolt spring migration
Nils, Teichert; Benitez, Jean-Philippe ULiege; Dierckx, Arnaud ULiege et al

in Aquatic Conservation (2020), 30

1. Changes in migration timing, resulting from the alteration in river continuity or the effect of climate change, can have major consequences on the population dynamics of diadromous fish. Forecasting ... [more ▼]

1. Changes in migration timing, resulting from the alteration in river continuity or the effect of climate change, can have major consequences on the population dynamics of diadromous fish. Forecasting the phenology of fish migration is thus critically important to implement management actions aimed at protecting fish during their migration. 2. In this study, an 11-year monitoring survey of Atlantic salmon smolts (Salmo salar) from the Ourthe River, Belgium, was analysed within a European Special Area of Conservation to improve the understanding of environment-induced spring migration. A logistic model was fitted to forecast smolt migration and to calculate phenological indicators for management, i.e. the onset, end, and duration of migration, while accounting for the influence of photoperiod, water temperature, and hydrological conditions. 3. The results indicated that the photo-thermal units accumulated by smolts above a 7 C temperature threshold was a relevant proxy to reflect the synergistic effect between temperature and photoperiod on smolt migration. After integrating the effect of river flow pulses, the model accurately explained the inter-annual changes in migration timing (R2 = 0.95). The model predictions provide decisive management information to identify sensitive periods during which mitigation measures (e.g. hydropower turbine shutdown, river discharge management) should be conducted to promote smolt survival. 4. The model was used to predict phenological characteristics under future scenarios of climate change. The results suggest a joint effect of hydrological alterations and water warming. Temperature increases of 1–4 C were associated with earlier initiation of migration, 6–51 days earlier, and spring flood events greatly influenced the duration of the migration period. Accordingly, the combined effects of human-induced modifications of the hydrological regimes and increasing temperatures could result in a mismatch between the smolt and favourable survival conditions in the marine environment. [less ▲]

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See detailAn Evaluation of Restocking Practice and Demographic Stock Assessment Methods for Cryptic Juvenile European Eel in Upland Rivers
Nzau Matondo, Billy ULiege; Benitez, Jean-Philippe ULiege; Dierckx, Arnaud ULiege et al

in Sustainability (2020), 12(1124),

Restocking of the critically endangered European eel Anguilla anguilla is widespread, but it is rarely scientifically evaluated. Methods used to assess its associated performance by estimating the ... [more ▼]

Restocking of the critically endangered European eel Anguilla anguilla is widespread, but it is rarely scientifically evaluated. Methods used to assess its associated performance by estimating the survival rate and implement restocking for maximum recruitment in rivers have not yet been investigated. Based on two glass eel restocking events using a single release site/point and multiple sites per river performed in upland rivers (>340 km from the North Sea), the recruitment success of stocked eels was scientifically evaluated during a 3-year study using multiple capture-mark-recapture methods and mobile telemetry. We compared the observed data with the data estimated from the Telemetry, De Lury and Jolly-Seber stock assessment methods. For recruitment data, Telemetry was very close to Jolly-Seber, an appropriate stock assessment method for open populations. Using the best model of Jolly-Seber, survival probability was higher (>95%) in both restocking practices, but recruitment yields were higher and densities of stocked eels were lower in multiple sites compared to a single site. Our results suggest that Telemetry can help to rapidly assess cryptic juvenile eel stocks with good accuracy under a limited number of capture-mark-recapture sessions. Artificial dispersal of glass eels on several productive habitats/sites per river appears to be the better-suited practice for restocking. [less ▲]

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See detailHow and where to pass? Atlantic salmon smolt’s behaviour at a hydropower station offering multiple migration routes
Renardy, Séverine ULiege; Benitez, Jean-Philippe ULiege; Tauzin, Amandine et al

in Hydrobiologia (2020), 847

We studied downstream migration behaviour of Atlantic salmon smolt at a hydropower station that offers four safe (weir, new incision gate on weir, downstream bypass, Archimedes screw) and one potentially ... [more ▼]

We studied downstream migration behaviour of Atlantic salmon smolt at a hydropower station that offers four safe (weir, new incision gate on weir, downstream bypass, Archimedes screw) and one potentially unsafe (Kaplan turbines) migration routes. We followed hatchery smolts using radio (n = 17) and RFID (n = 200) telemetry. They were released 1.2 km upstream of the hydropower station in spring 2018, in four groups, at different water discharge (18 to 37.2 m3s-1) and temperature (12.2–17.6 °C) conditions. For radio-tagged smolts, the repartition of the migration routes was 41.2% for the bypass, 17.6% for both the Kaplan turbine and the weir, 11.8% for the Archimedes screw, 0% for the new incision and 11.8% of unknown route. For the RFID-tagged smolts, the repartition was 38.0% for the bypass, 56.5% for the weir and/or the Kaplan, 4.5% for the new incision and 1.0% for the Archimedes Screw. The median time to cross the hydropower station was 58 min, and 88.2% of the smolts succeed to continue their downstream migration. The results demonstrate a diversity of choices of migration routes and underline the importance to optimise the position of fish-friendly turbines and fish passes at hydropower stations to increase their attractiveness. [less ▲]

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See detailRapport final annuel 2020 au Service Public de Wallonie (DGARNE/DNF-SP) de la Subvention 2019-2020 relative au suivi scientifique de la réhabilitation du saumon atlantique dans le bassin de la Meuse
Benitez, Jean-Philippe ULiege; Erraud, Alexandre; Dierckx, Arnaud ULiege et al

Report (2020)

Le présent rapport d’activités intègre les travaux des deux équipes universitaires de Namur et de Liège dans la cadre de la convention relative à la réhabilitation du saumon atlantique dans le bassin de ... [more ▼]

Le présent rapport d’activités intègre les travaux des deux équipes universitaires de Namur et de Liège dans la cadre de la convention relative à la réhabilitation du saumon atlantique dans le bassin de la Meuse pour la période février 2019 - janvier 2020. [less ▲]

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See detailÉvaluation de la qualité biologique des rivières wallonnes sur base des indices biologiques poissons. Support technique aux inventaires 2019
Dierckx, Arnaud ULiege; Benitez, Jean-Philippe ULiege; Rimbaud, Gilles ULiege et al

Report (2019)

Ce document reprend les informations recueillies dans le cadre d’un travail effectué par l’Université de Liège pour le compte du Service public de Wallonie-DEMNA et financé dans le cadre d’un marché ... [more ▼]

Ce document reprend les informations recueillies dans le cadre d’un travail effectué par l’Université de Liège pour le compte du Service public de Wallonie-DEMNA et financé dans le cadre d’un marché public de services qui a pour objectif l’évaluation de la qualité biologique des eaux de surface basée sur les indices biologiques « poissons » dans onze cours d’eau de Wallonie. [less ▲]

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See detailTesting three stock assessment methods to evaluate the reintroduction success of the cryptic european eel anguilla Anguilla L.
Nzau Matondo, Billy ULiege; Benitez, Jean-Philippe ULiege; Dierckx, Arnaud ULiege et al

Poster (2019, September)

Glass eel stocking in rivers as conservation measure is usual, but methods to assess the associate performance by estimating precisely the survival rate are not investigated yet. From 2013 to 2019 ... [more ▼]

Glass eel stocking in rivers as conservation measure is usual, but methods to assess the associate performance by estimating precisely the survival rate are not investigated yet. From 2013 to 2019, scientific stocking tests have been implemented in Belgian rivers (>300 km from the estuary). Two release events, cohort 2013 (density 1-1.5 kg released at a single release point) and cohort 2017 (density 2.4 kg/ha dispersed over sites spaced from 250 m) were conducted in eight typologically different rivers. One reference site per release campaign, with the best recruitment level was selected to test different stock assessment methods. We used both multiple capture-mark-recapture sessions (CMR; cohort 2013: n = 4155 glass eels, 5 sessions in 2014-2019; cohort 2017: n = 1586 glass eels, 4 sessions in 2017-2019) in combination with mobile RFID-Telemetry investigations, over 200-m long river stretches. We compared the observed data with the data corrected using: (i) ratio between RFID detection and electrofishing (DCM), (ii) number of eels captured in a capture session using the DeLury model (DLM) and, (iii) multiple CMR occasions for open-population Jolly-Seber model (JSM). Eel density estimation was close between release techniques. JSM data were close to DCM data and estimated time-varying capture probability, survival probability between sessions and super-population abundances. Our results suggest multiple CMR campaigns with applying JSM were better-suited methodology to assess juvenile eel cryptic stocks, but DCM helped to rapidly assessing stock under limited CMR occasions. Glass eel release on several sites seems to be the best stocking technique. [less ▲]

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See detailÉtude du franchissement de la passe à poissons de Bomal s/ Ourthe, sur l’Aisne
Watthez, Quentin; Lerquet, Marc; Sonny, Damien et al

Report (2019)

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See detailRehabilitation effort for anadromous salmonids in the river Meuse basin. Achievements and new challenges
Ovidio, Michaël ULiege; Kestemont, Patrick; Dierckx, Arnaud ULiege et al

Conference (2019, May)

Until the end of the 19th century, the Atlantic salmon (Salmo salar) was widespread in the river Meuse basin and salmon fisheries were prosperous in France, Belgium and The Netherlands. The number of ... [more ▼]

Until the end of the 19th century, the Atlantic salmon (Salmo salar) was widespread in the river Meuse basin and salmon fisheries were prosperous in France, Belgium and The Netherlands. The number of salmon and sea trout captures reaches 57000 ind/year in the Dutch Rhine-Meuse delta. Between 1840 and 1950, the building of navigation dams in the river Meuse and its tributaries, as well as the increase of industrial water pollution and the overexploitation of the stock, led to the extinction of all anadromous fish species. In 1983, the capture of a sea trout (Salmo trutta) in the lower Belgian Meuse brought the problem of the migratory of fish to the surface. Based on scientific advices and feasibility studies carried out from 1983 to 1986, the program Salmon Meuse was launch in 1987. It aims at the restoration of the complete life cycle of migratory salmonids in the international River Meuse Basin. Important rehabilitation efforts have been progressively done since the beginning of the project to the present 1) Improvement of the general quality of the water 2) Restocking with strains originating from France, Ireland, Scotland 3) Hydromorphological restoration of gravel bed habitats 4) The construction of modern fishways for upstream migration in the Meuse and tributaries 5) Adoption of measures to facilitate downstream migration at hydroelectric sites 6) Development of a salmon hatchery with facilities to realise artificial reproduction using returning adults 7) The establishment of international collaboration network 8) The election of the best strains based on genetics of returning adults and the process of smoltification finally 9) The opening of the Haringvliet sluices in the Estuary of the Meuse in the Netherland in 2018. In the year 2000, the first adult salmon originating from restocking program was captured in the fishway of Lixhe, and this return of a salmon, more than 50 years of his extinction, was a major ecological event. From 2000 to 2018, the number of returning Atlantic salmon and sea trout progressively increased and reaches n=60 in the best year. This underline partial achievement of the objectives of the project, but the number of returning adult is sill too low to have a natural sustainable population. Supplementary efforts must be undertaken in the future, especially in terms of success of smolts downstream migration and escapement success as well as an optimization of the restocking practices (in terms of quantity and choice of the best development stage). During our talk, we will synthesise the major key-points of this challenging project whose success requires a balance between the development and maintenance of numerous human activities and the associate preservation of the aquatic environment. We will use examples of results originating from recent scientific research. [less ▲]

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See detailRapport de convention sur la Réhabilitation du Saumon Atlantique dans le bassin de la Meuse
Benitez, Jean-Philippe ULiege; Dierckx, Arnaud ULiege; Nzau Matondo, Billy ULiege et al

Report (2019)

Le présent rapport d’activités intègre les travaux (2018-2019) des deux équipes universitaires de Namur et de Liège dans la cadre de la convention relative à la réhabilitation du saumon atlantique dans le ... [more ▼]

Le présent rapport d’activités intègre les travaux (2018-2019) des deux équipes universitaires de Namur et de Liège dans la cadre de la convention relative à la réhabilitation du saumon atlantique dans le bassin de la Meuse [less ▲]

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See detailWhat happens to glass eels after restocking in upland rivers? A long‐term study on their dispersal and behavioural traits
Nzau Matondo, Billy ULiege; Séleck, Emilie; Dierckx, Arnaud ULiege et al

in Aquatic Conservation (2019)

The European eel Anguilla anguilla is a critically endangered fish species as a result of human activities and climate change in river and oceanic ecosystems. Restocking using glass eels in continental ... [more ▼]

The European eel Anguilla anguilla is a critically endangered fish species as a result of human activities and climate change in river and oceanic ecosystems. Restocking using glass eels in continental freshwater areas is a potential conservation measure for enhancing local eel stocks and for conserving the species in aquatic habitats, where it may otherwise disappear. However, little is known about the fate of these restocked individuals and the early ecological behaviour of the young eels translocated in rivers.A portable radio‐frequency identification (RFID) telemetry system and 12‐mm tags were used to track restocked eels for a duration of 4 years. The aim was to understand the early movement, behavioural traits, dispersal, and habitat use of elvers after restocking performed in 2013 with glass eels in a shallow riverine environment.From the 241 tagged eels (total length, Q50 = 152 mm), 85% were detected in 1968 positions during a period of 4 years, beginning in 2014. Clear seasonality in eel activity was observed, with higher mobility in summer when the water temperature was high (above 12°C). Dispersal was slowed by numerous artificial obstacles and the high carrying capacity of habitats. There was a negative relationship between the body size of eels at tagging and their mobility. Five behavioural categories of mobility patterns were identified: ascending, descending, oscillating with an upstream trend, oscillating with a downstream trend, and stationary. The first four categories depleted with time, in favour of stationary individuals that displayed a highly sedentary lifestyle.This study provides new knowledge of the long‐term dispersal behaviour of restocked eels and the influence of seasons, barriers, and habitats on their colonization strategy changing with time. The results contribute to a better understanding of the issue of uncommon restocking practices in upland rivers. [less ▲]

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See detailEvaluation de la qualité biologique des rivières wallonnes sur base des indices biologiques poissons
Dierckx, Arnaud ULiege; Benitez, Jean-Philippe ULiege; Rimbaud, Gilles ULiege et al

Report (2018)

Ce document reprend les informations recueillies dans le cadre d’un travail effectué par l’Université de Liège pour le compte du Service public de Wallonie-DEMNA et financé dans le cadre d’un marché ... [more ▼]

Ce document reprend les informations recueillies dans le cadre d’un travail effectué par l’Université de Liège pour le compte du Service public de Wallonie-DEMNA et financé dans le cadre d’un marché public de services qui a pour objectif l’évaluation de la qualité biologique des eaux de surface basée sur les indices biologiques « poissons » dans seize cours d’eau de Wallonie. [less ▲]

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See detailMovement behaviours of potamodromous fish within a large anthropised river after the reestablishment of the longitudinal connectivity
Benitez, Jean-Philippe ULiege; Dierckx, Arnaud ULiege; Nzau Matondo, Billy ULiege et al

in Fisheries Research (2018), 207

Human activity has caused longitudinal fragmentation of many rivers. Fishways have been installed worldwide, but their successive use by potamodromous species remains poorly documented, particularly in ... [more ▼]

Human activity has caused longitudinal fragmentation of many rivers. Fishways have been installed worldwide, but their successive use by potamodromous species remains poorly documented, particularly in large river ecosystems. Four vertical slot fishways were installed within a 32-km stretch of the lower Belgian Meuse River basin. From 2012 to 2016, n=532 individuals belonging to 11 potamodromous fish species (rheophilic, limnophilic and large carnivorous) were continuously captured in the most downstream fishway (M0), tagged with an RFID transponder and released upstream. These could be further detected in upstream river part within three fishways (M1 and M2 in the Meuse, and O1 in an important tributary, the Ourthe) that were equipped with RFID detection stations. In the first downstream stretch (13 km from M0 to M1) we quantified an ascending rate until M1 (number of individuals detected in M1/ number of individuals tagged in M0) of 32.9% including all individuals tagged, with a maximum value of 67.2% for chub (Squalius cephalus), 40% for pike (Esox Lucius) and 35.5% for nase (Chondrostoma nasus), and a progression time M0 to M1 of 1.1 days per kilometre (d/km), with trout (Salmo trutta) as the fastest species (0.3 d/km). Upstream of the M1 fishway, many individuals of rheophilic species (trout and barbel, Barbus barbus) preferred to enter in the Ourthe tributary (detection at the Ourthe fishway) unlike the upstream Meuse (detection at the most upstream fishway in the Meuse), demonstrating a new accessibility to more adapted spawning sites. Most fish were present within fishways mainly in spring during the circum-spawning migration, and during summer and autumn for dispersal and/or seeking-refuge. The diel activity cycle varied depending on the species, with detection during the entire diel cycle (e.g. chub and barbel), during the day (e.g. trout) and during the night (e.g. catfish, Silurus glanis). The installation of fishways in the degraded river Meuse can be considered adequate for the restoration of the free movement because potamodromous species demonstrated their ability to migrate over long distances (> 20 km) and to reach potential spawning habitats through the reopened access to a tributary. [less ▲]

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See detailEtude du franchissement de 3 passes à poissons sur la Vesdre aval en 1° catégorie
Watthez, Quentin; Goffaux, Delphine; Sonny, Damien et al

Report (2018)

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See detailRapport de convention sur la Réhabilitation du Saumon Atlantique dans le bassin de la Meuse
Ovidio, Michaël ULiege; Dierckx, Arnaud ULiege; Benitez, Jean-Philippe ULiege et al

Report (2018)

Le présent rapport d’activités intègre les travaux des deux équipes universitaires de Namur et de Liège dans la cadre de la convention relative à la réhabilitation du saumon atlantique dans le bassin de ... [more ▼]

Le présent rapport d’activités intègre les travaux des deux équipes universitaires de Namur et de Liège dans la cadre de la convention relative à la réhabilitation du saumon atlantique dans le bassin de la Meuse. [less ▲]

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